US airport delays

What is disrupted right now, from the FAA's live status feed, and how often flights actually ran late, from the Department of Transportation's flight-by-flight records, which arrive about two to three months after the month ends. Back to World Pulse.

Live now — FAA · checked 08:00 UTC

No ground stops, delay programs or reported delays in effect.
6 closure / restriction notices (mostly NOTAMs limiting some aircraft)
LFTClosure!LFT 10/043 LFT AD AP CLSD DLY 0430-0915 2610190430-2610200915
SNAClosure!SNA 10/025 SNA AD AP CLSD DLY 0630-1315 2610200630-2610231315
ASERestricted (NOTAM)!ASE 10/116 ASE AD AP CLSD EXC LIFE FLT HEL AND SAR HEL 30MIN PPR 970-379-8406 2610200500-2610201300
LAXRestricted (NOTAM)!LAX 05/277 LAX AD AP CLSD TO NON SKED TRANSIENT GA ACFT EXC 24HR PPR CTC ATLANTIC AVIATION 310-258-9884 OR SIGNATURE AVIATION 310-410-9605 2605271826-2705281600
LGARestricted (NOTAM)!LGA 10/238 LGA AD AP CLSD EXC HEL 30MIN PPR 718-533-3700 2610200414-2610201000
SANRestricted (NOTAM)!SAN 10/004 SAN AD AP CLSD TO NON SKED TRANSIENT GA ACFT EXC PPR 619-298-7704 2610011633-2701010800
Month Jul 2026 Jun 2026 May 2026 Apr 2026 Mar 2026 Feb 2026 Jan 2026 Dec 2025 Nov 2025 Oct 2025 Sep 2025 Aug 2025 Jul 2025 Measure Departures Arrivals
15%45%+ of departures 15+ min late dot size = flights · ring = FAA program live now

Nationally, May 2026

22.2%
of 606,080 departures ran 15+ min late · usual for May: 21.3% · 0.9% cancelled
Last 37 months · dashed = usual for that month (median of up to 5 earlier years, 2020 left out)
Where late-arrival minutes came from
Late aircraft 40%
Airline 33%
Air traffic 20%
Weather 6%
Security 0%

Airports, May 2026 (departures)

AirportCityFlightsLate 15+ vs usual CancelledAvg minMain cause
ORD Chicago, IL 33,733 23.3% +4.5 1.0% 18 Late aircraft
ATL Atlanta, GA 27,535 22.2% +1.8 1.2% 15 Airline
DFW Dallas/Fort Worth, TX 27,419 28.9% +5.2 3.3% 22 Late aircraft
DEN Denver, CO 27,406 23.9% -5.2 0.3% 15 Late aircraft
PHX Phoenix, AZ 17,337 25.2% +4.8 0.3% 16 Late aircraft
LAX Los Angeles, CA 16,317 20.4% +3.3 0.5% 14 Late aircraft
CLT Charlotte, NC 15,778 23.3% +0.9 0.3% 16 Late aircraft
LAS Las Vegas, NV 14,585 29.6% +3.0 0.7% 19 Late aircraft
SEA Seattle, WA 14,564 19.8% +3.0 0.4% 12 Airline
SFO San Francisco, CA 13,114 31.7% +14.2 0.8% 22 Late aircraft
MCO Orlando, FL 12,958 24.5% -3.8 0.7% 16 Late aircraft
BOS Boston, MA 12,694 18.0% -4.2 0.6% 13 Late aircraft
DCA Washington, DC 12,158 23.7% -0.7 1.4% 18 Late aircraft
LGA New York, NY 11,375 22.0% +1.4 1.8% 17 Late aircraft
MSP Minneapolis, MN 10,400 16.5% -1.0 0.5% 13 Airline
EWR Newark, NJ 10,300 12.8% -10.9 0.9% 10 Airline
SLC Salt Lake City, UT 10,146 14.8% +0.5 0.4% 9 Airline
DTW Detroit, MI 10,112 18.7% +1.0 1.3% 14 Airline
IAH Houston, TX 10,105 24.5% -2.4 0.5% 19 Late aircraft
BNA Nashville, TN 9,814 34.4% +12.6 0.6% 20 Late aircraft
MIA Miami, FL 9,296 24.2% -0.7 0.5% 17 Late aircraft
PHL Philadelphia, PA 9,251 19.2% -0.5 1.1% 15 Late aircraft
SAN San Diego, CA 8,947 25.7% +8.7 0.7% 15 Late aircraft
JFK New York, NY 8,535 16.1% -4.5 1.1% 13 Late aircraft
BWI Baltimore, MD 8,161 28.5% -0.7 0.3% 17 Late aircraft
AUS Austin, TX 7,831 28.5% +7.7 0.9% 21 Late aircraft
TPA Tampa, FL 6,471 25.7% +3.5 0.7% 20 Late aircraft
FLL Fort Lauderdale, FL 6,437 25.4% -0.1 0.5% 17 Late aircraft
MDW Chicago, IL 6,269 31.5% +7.4 0.4% 17 Late aircraft
DAL Dallas, TX 6,141 42.2% +8.7 1.7% 26 Late aircraft
PDX Portland, OR 5,535 16.0% +2.5 0.4% 11 Airline
IAD Washington, DC 5,474 13.3% -4.4 0.6% 13 Late aircraft
STL St. Louis, MO 5,375 26.2% +3.1 0.8% 19 Late aircraft
HNL Honolulu, HI 4,953 16.2% +0.8 1.1% 10 Airline
SMF Sacramento, CA 4,945 20.6% +3.2 0.4% 12 Late aircraft
RDU Raleigh/Durham, NC 4,884 18.2% -0.8 0.9% 14 Late aircraft
HOU Houston, TX 4,533 35.2% +9.4 0.8% 19 Late aircraft
MCI Kansas City, MO 4,354 23.3% +4.9 1.1% 16 Late aircraft
IND Indianapolis, IN 4,324 18.5% +1.6 0.9% 12 Late aircraft
MSY New Orleans, LA 4,194 29.0% +6.8 0.8% 21 Late aircraft
CMH Columbus, OH 3,860 16.2% -3.8 1.2% 12 Late aircraft
SNA Santa Ana, CA 3,835 19.9% +0.8 0.8% 14 Late aircraft
PIT Pittsburgh, PA 3,778 15.9% -1.1 0.8% 12 Late aircraft
CLE Cleveland, OH 3,745 14.8% -4.2 1.0% 13 Late aircraft
SJC San Jose, CA 3,686 19.3% +3.6 0.4% 10 Late aircraft
SAT San Antonio, TX 3,485 22.6% +5.5 1.4% 18 Late aircraft
CVG Cincinnati, OH 3,064 15.9% -3.3 1.0% 12 Late aircraft
SJU San Juan, PR 2,875 16.9% -7.3 0.2% 12 Late aircraft
RSW Fort Myers, FL 2,802 18.6% -1.9 0.5% 15 Late aircraft
JAX Jacksonville, FL 2,744 19.9% -1.1 1.0% 19 Airline
MKE Milwaukee, WI 2,735 18.2% +4.5 0.7% 13 Airline
OAK Oakland, CA 2,683 26.1% +7.5 0.6% 14 Late aircraft
PBI West Palm Beach/Palm Beach, FL 2,545 18.7% -6.7 1.0% 15 Late aircraft
BUR Burbank, CA 2,520 22.7% +6.3 1.1% 15 Late aircraft
SDF Louisville, KY 2,304 16.9% -2.9 0.9% 13 Airline
ONT Ontario, CA 2,298 20.8% +3.7 0.7% 13 Late aircraft
MEM Memphis, TN 2,228 22.1% +0.4 1.1% 19 Airline
OMA Omaha, NE 2,223 19.3% +3.8 0.6% 15 Late aircraft
CHS Charleston, SC 2,200 18.4% -2.9 0.7% 16 Late aircraft
OGG Kahului, HI 2,178 13.0% -1.8 0.8% 7 Late aircraft
ABQ Albuquerque, NM 2,151 21.0% +2.4 0.7% 15 Late aircraft
OKC Oklahoma City, OK 2,102 22.4% +5.4 1.2% 15 Late aircraft
BOI Boise, ID 2,040 19.5% +6.7 0.2% 14 Late aircraft
BDL Hartford, CT 1,981 14.0% -4.4 0.7% 11 Late aircraft
BUF Buffalo, NY 1,936 18.4% +0.7 0.7% 13 Late aircraft
ANC Anchorage, AK 1,818 13.3% +2.9 0.6% 9 Airline
SAV Savannah, GA 1,803 19.3% -5.7 1.1% 15 Airline
ORF Norfolk, VA 1,790 17.6% -2.2 0.8% 15 Airline
GRR Grand Rapids, MI 1,726 15.2% -0.6 0.8% 15 Airline
RNO Reno, NV 1,708 20.1% +4.6 0.7% 14 Air traffic
TUS Tucson, AZ 1,691 19.4% +2.7 0.5% 16 Airline
TUL Tulsa, OK 1,626 21.5% +4.1 1.2% 19 Late aircraft
RIC Richmond, VA 1,623 18.4% +0.1 0.8% 14 Late aircraft
BHM Birmingham, AL 1,550 20.8% -1.7 1.2% 16 Airline
GEG Spokane, WA 1,542 12.7% -0.3 0.5% 9 Airline
SRQ Sarasota/Bradenton, FL 1,513 19.3% -1.1 0.5% 18 Airline
DSM Des Moines, IA 1,382 17.4% +3.1 1.2% 16 Late aircraft
LIH Lihue, HI 1,372 16.6% +5.5 1.5% 11 Late aircraft
PVD Providence, RI 1,366 17.9% -1.7 0.6% 12 Late aircraft
ELP El Paso, TX 1,357 23.5% +4.3 0.9% 18 Late aircraft
KOA Kona, HI 1,353 12.6% -0.0 1.0% 7 Late aircraft
PNS Pensacola, FL 1,320 24.0% +3.8 1.3% 18 Late aircraft
XNA Fayetteville, AR 1,319 18.0% -0.9 1.3% 20 Late aircraft
TYS Knoxville, TN 1,308 19.5% +4.7 1.1% 17 Airline
MSN Madison, WI 1,305 15.5% -0.1 1.3% 17 Airline
GSP Greer, SC 1,302 17.3% +2.6 1.1% 12 Late aircraft
LIT Little Rock, AR 1,215 20.3% +0.1 1.0% 17 Late aircraft
PSP Palm Springs, CA 1,215 23.2% +6.8 0.8% 19 Air traffic
ALB Albany, NY 1,186 14.5% -4.4 0.8% 12 Airline
LGB Long Beach, CA 1,184 18.6% -0.3 0.1% 9 Late aircraft
MYR Myrtle Beach, SC 1,132 18.1% -0.5 1.0% 14 Late aircraft
COS Colorado Springs, CO 1,119 19.5% +0.6 0.9% 17 Airline
FAT Fresno, CA 1,117 18.9% +2.0 0.6% 18 Airline
VPS Valparaiso, FL 1,098 24.8% +4.0 0.9% 18 Late aircraft
PWM Portland, ME 1,056 13.5% -1.5 0.9% 10 Late aircraft
ECP Panama City, FL 1,021 24.6% +2.0 1.5% 17 Late aircraft
ICT Wichita, KS 1,007 21.7% +2.7 1.3% 17 Late aircraft
97 airports with 1,000+ flights this month, busiest first. Click a header to sort.

Airlines — arrivals 15+ min late

AirlineFlightsLateCanc.
Republic32,20315.6%1.4%
Alaska29,18416.8%0.7%
Envoy28,80616.9%1.8%
Delta91,95517.8%1.2%
JetBlue19,80618.6%0.2%
SkyWest75,99419.9%0.9%
United74,20020.0%0.4%
PSA20,85423.3%1.9%
Frontier18,42323.3%0.5%
American88,74023.5%1.5%
Allegiant10,57027.1%0.2%
Southwest120,64627.6%0.4%
Spirit35431.6%14.1%
Regional airlines (SkyWest, Envoy, Republic, PSA…) fly under the big brands' names.

Worst days this month

DateAirportLateCanc.
05-19DAL 64%24%
05-01IAH 72%3%
05-18STL 68%7%
05-23IAH 70%0%
05-19DFW 53%35%
05-18MDW 68%2%
05-18ORD 64%12%
05-10DFW 54%30%
05-18LAS 63%1%
05-21DAL 62%0%
Ranked by share of flights late or cancelled; airports with 150+ flights that day.

FAA programs and delays, last 7 days

AirportWhatStarted (UTC)HoursPeak avgReason
SANDeparture delays 10-20 01:30 1.8 16 min VOL:Compacted Demand
LASGround delay program 10-20 01:00 6.2 48 min other
BOSDeparture delays 10-19 23:00 6.2 16 min RWY:Construction
LGADeparture delays 10-19 20:30 1.5 16 min VOL:Compacted Demand
DCAGround stop 10-19 20:00 0.7 — VIP
LASDeparture delays 10-19 19:00 0.5 16 min WX:Wind
YULGround delay program 10-19 18:00 5.2 79 min runway construction
YULGround delay program 10-19 16:00 1.7 49 min other
LASDeparture delays 10-19 14:45 0.3 16 min OTHER:INDIVIDUAL RELEASES
PHLDeparture delays 10-19 13:45 1.5 16 min VOL:Compacted Demand
TEBDeparture delays 10-19 13:45 1.3 16 min RWY:Maintenance
SANGround delay program 10-19 13:15 15.5 54 min airport volume
SFOGround delay program 10-19 12:45 7.3 55 min low ceilings
SFOGround delay program 10-19 04:00 2.0 58 min low ceilings
SFOGround stop 10-19 03:15 0.8 — low ceilings
LASDeparture delays 10-19 01:00 1.0 16 min WX:Wind
SANGround delay program 10-19 00:45 3.8 52 min airport volume
BOSArrival delays 10-18 20:45 4.5 16 min ZBW / RWY:Construction
LASGround delay program 10-18 19:45 5.3 70 min aircraft emergency
SNADeparture delays 10-18 19:30 2.0 61 min VOL:Compacted Demand
LASDeparture delays 10-18 18:30 1.8 16 min RWY:Disabled Aircraft
LASGround stop 10-18 18:15 1.5 — aircraft emergency
PHXDeparture delays 10-18 18:00 0.2 16 min VOL:Multi-taxi
YULGround delay program 10-18 17:00 5.7 20 min other
PHXDeparture delays 10-18 16:15 0.8 16 min VOL:Multi-taxi
AUSGround delay program 10-18 15:00 6.8 39 min runway construction
SANGround delay program 10-18 14:00 6.0 38 min airport volume
OPFDeparture delays 10-18 13:15 0.3 16 min VOL:Compacted Demand
TEBDeparture delays 10-18 13:15 6.8 76 min STAFF:Staffing
JFKDeparture delays 10-18 01:15 1.3 16 min VOL:Compacted Demand
YVRGround delay program 10-18 00:00 4.5 18 min equipment outage
BOSDeparture delays 10-17 23:15 0.2 16 min RWY:Construction
FLLDeparture delays 10-17 23:15 0.2 16 min TM Initiatives:MIT:WX
MIADeparture delays 10-17 23:00 3.5 31 min TM Initiatives:MIT:WX
BOSDeparture delays 10-17 21:45 0.5 16 min RWY:Construction
LGADeparture delays 10-17 20:45 4.8 76 min TM Initiatives:SWAP:WX
EWRDeparture delays 10-17 20:30 3.0 76 min TM Initiatives:SWAP:WX
LGAGround stop 10-17 20:00 0.5 — wind
EWRArrival delays 10-17 20:00 0.5 31 min ZDC / WX: SEV TURB
TEBDeparture delays 10-17 20:00 3.5 61 min TM Initiatives:SWAP:WX
JFKGround stop 10-17 19:45 1.5 — wind
EWRGround stop 10-17 19:45 1.0 — wind
MIADeparture delays 10-17 19:45 0.8 16 min RWY:Construction
SEADeparture delays 10-17 19:30 2.8 16 min RWY:Construction
SANDeparture delays 10-17 19:00 1.2 16 min VOL:Compacted Demand
EWRGround delay program 10-17 17:00 9.8 67 min other
MCODeparture delays 10-17 16:45 2.3 16 min TM Initiatives:MIT:VOL
MIADeparture delays 10-17 16:45 2.5 61 min RWY:Construction
YVRGround delay program 10-17 16:15 3.0 15 min other
PHXDeparture delays 10-17 16:15 0.7 16 min VOL:Multi-taxi
RSWDeparture delays 10-17 15:45 3.3 16 min WX:Thunderstorms
MIADeparture delays 10-17 14:45 1.3 31 min RWY:Construction
SANGround delay program 10-17 14:00 11.0 53 min airport volume
TEBDeparture delays 10-17 10:30 0.2 16 min INDIVIDUAL RELEASE
LASGround stop 10-17 05:45 0.8 — STAFFING
SANGround stop 10-17 00:45 1.0 — wind
SFOGround delay program 10-17 00:45 3.5 50 min other
YVRGround stop 10-16 23:45 0.8 — OCL:
MCODeparture delays 10-16 23:45 8.0 16 min RWY:Maintenance
BWIDeparture delays 10-16 23:15 8.5 91 min WX:Thunderstorms
LGAGround stop 10-16 22:45 2.3 — thunderstorms
EWRDeparture delays 10-16 22:45 5.3 91 min TM Initiatives:SWAP:WX
BWIGround stop 10-16 22:30 2.0 — thunderstorms
PHXGround delay program 10-16 22:30 5.8 65 min other
IADGround stop 10-16 22:15 1.2 — thunderstorms
DCAGround stop 10-16 22:15 3.0 — thunderstorms
EWRGround stop 10-16 22:15 3.2 — STAFFING
IADDeparture delays 10-16 22:15 5.8 76 min WX:Thunderstorms
PHLDeparture delays 10-16 22:00 6.0 91 min TM Initiatives:SWAP:WX
SFODeparture delays 10-16 21:45 1.3 46 min RWY:Construction
PHLGround stop 10-16 21:15 1.0 — thunderstorms
TEBGround stop 10-16 21:15 2.3 — thunderstorms
JFKGround delay program 10-16 20:30 6.0 60 min thunderstorms
EWRGround delay program 10-16 20:15 6.2 169 min other
LGADeparture delays 10-16 20:15 7.8 136 min TM Initiatives:SWAP:WX
SFODeparture delays 10-16 20:15 0.5 31 min VOL:Multi-taxi
FLLDeparture delays 10-16 19:45 0.7 16 min TM Initiatives:MIT:WX
BOSGround stop 10-16 19:30 0.5 — low ceilings
LASGround stop 10-16 19:15 1.0 — runway maintenance
LGADeparture delays 10-16 18:30 0.5 16 min TM Initiatives:SWAP:WX
SNADeparture delays 10-16 18:30 2.2 16 min VOL:Compacted Demand
MSPGround stop 10-16 18:00 0.7 — wind
TEBDeparture delays 10-16 18:00 10.0 76 min TM Initiatives:SWAP:WX
SNADeparture delays 10-16 17:30 0.2 16 min WX:Wind
SANGround stop 10-16 17:15 2.0 — airport departure volume
YULGround delay program 10-16 17:00 7.2 64 min runway maintenance
SANDeparture delays 10-16 17:00 3.7 31 min WX:Wind
LASGround delay program 10-16 16:45 13.8 80 min wind
SANGround delay program 10-16 16:30 12.2 152 min wind
DFWDeparture delays 10-16 16:30 1.0 16 min WX:Wind
PHXDeparture delays 10-16 16:30 0.2 16 min VOL:Multi-taxi
LGAGround delay program 10-16 16:00 12.0 107 min thunderstorms
IAHDeparture delays 10-16 16:00 0.2 16 min WX:Wind
SANGround stop 10-16 15:45 0.8 — wind
PHLGround delay program 10-16 15:45 8.5 57 min thunderstorms
AUSGround delay program 10-16 15:15 7.0 66 min runway construction
AUSGround stop 10-16 15:00 0.2 — runway construction
TEBDeparture delays 10-16 15:00 0.5 31 min TM Initiatives:SWAP:WX
DFWDeparture delays 10-16 14:30 0.8 16 min WX:Wind
EWRDeparture delays 10-16 14:15 0.8 46 min TM Initiatives:SWAP:WX
PHLDeparture delays 10-16 14:15 2.5 46 min WX:Thunderstorms
DCAGround delay program 10-16 12:30 15.5 211 min thunderstorms
BOSGround delay program 10-16 12:15 12.5 101 min low ceilings
EWRDeparture delays 10-16 12:00 1.2 46 min TM Initiatives:SWAP:WX
BHMGround delay program 10-16 06:00 0.2 7 min equipment outage
SEAGround stop 10-16 02:30 0.7 — runway construction
DFWGround stop 10-16 02:15 0.5 — wind
SEADeparture delays 10-16 01:30 0.2 16 min RWY:Construction
ORDGround delay program 10-16 00:45 3.3 81 min other
DFWGround delay program 10-15 23:45 3.0 51 min thunderstorms
BOSDeparture delays 10-15 23:30 2.8 31 min RWY:Construction
SEADeparture delays 10-15 23:30 0.2 16 min RWY:Construction
ORDGround stop 10-15 23:15 1.5 — thunderstorms
DFWGround stop 10-15 22:15 1.5 — wind
YYCGround delay program 10-15 22:00 2.7 31 min runway construction
ORDDeparture delays 10-15 21:45 4.5 16 min WX:Low Ceilings
BFIDeparture delays 10-15 19:00 0.3 16 min VOL:Volume
TEBDeparture delays 10-15 19:00 2.8 31 min VOL:Multi-taxi
SFODeparture delays 10-15 18:30 1.0 16 min VOL:Multi-taxi
PHXDeparture delays 10-15 16:15 0.8 16 min VOL:Multi-taxi
SANDeparture delays 10-15 16:15 10.0 46 min VOL:Compacted Demand
SEADeparture delays 10-15 16:15 0.3 16 min RWY:Construction
SFOGround stop 10-15 16:00 0.8 — airport volume
YULGround delay program 10-15 16:00 7.2 17 min runway construction
MIADeparture delays 10-15 15:30 0.7 16 min RWY:Construction
SEAGround stop 10-15 15:15 1.3 — low visibility
SEADeparture delays 10-15 15:00 0.2 16 min WX:Fog
DENGround stop 10-15 14:15 1.0 — low ceilings
SANGround delay program 10-15 14:00 14.8 39 min airport volume
DFWDeparture delays 10-15 14:00 1.2 46 min WX:Thunderstorms
TEBDeparture delays 10-15 13:45 0.8 16 min VOL:Multi-taxi
YVRGround stop 10-15 13:00 0.7 — fog
BOSGround delay program 10-15 11:45 7.5 12 min runway construction
DFWDeparture delays 10-15 00:15 2.5 16 min WX:Thunderstorms
JFKDeparture delays 10-14 23:45 1.3 16 min RWY:Construction
BWIDeparture delays 10-14 23:30 2.0 46 min WX:Thunderstorms
BWIDeparture delays 10-14 22:45 0.5 16 min WX:Thunderstorms
DALDeparture delays 10-14 21:45 0.3 16 min WX:Thunderstorms
DFWDeparture delays 10-14 21:15 1.0 16 min WX:Thunderstorms
DALDeparture delays 10-14 21:00 0.2 16 min WX:Thunderstorms
LASDeparture delays 10-14 21:00 1.2 16 min STAFF:Staffing
DFWDeparture delays 10-14 20:30 0.2 16 min WX:Thunderstorms
DALDeparture delays 10-14 20:15 0.5 16 min WX:Thunderstorms
BOSGround stop 10-14 20:00 0.7 — runway construction
DENGround delay program 10-14 19:45 7.2 61 min low ceilings
DALDeparture delays 10-14 19:15 0.5 31 min WX:Thunderstorms
YULGround delay program 10-14 18:29 4.5 12 min airport volume
BOSGround delay program 10-14 18:29 4.8 66 min runway construction
AUSGround delay program 10-14 18:29 4.8 59 min runway construction
SANDeparture delays 10-14 18:29 1.0 31 min VOL:Compacted Demand

Most disrupted, last 30 days (FAA)

AirportGSGDPDelayHours
SAN36585
BOS23540
LAS33533
YUL06032
EWR22531
LGA21429
TEB10828
PHL11320
DCA21019
AUS13019
SFO23317
BWI10313
DFW21612
MCO00210
JFK11210
Recording since 2026-10-14. The FAA keeps no public history, so this is only what we have polled (every 15 minutes).
Sources. Delay rates: US DOT Bureau of Transportation Statistics, Reporting Carrier On-Time Performance (public domain). It covers domestic flights on airlines with at least 0.5% of US domestic passenger revenue, about 600,000 flights a month; smaller carriers and international flights are not in it. Live status: FAA Air Traffic Control System Command Center, NAS Status (public domain). Airport locations: OurAirports (public domain).
Definitions. Late means 15+ minutes after schedule, out of flights that operated. Causes are reported by airlines for arrivals 15+ minutes late. "Late aircraft" is the knock-on from an earlier delay to the same plane, so it says nothing about where the trouble started. "Air traffic" (the NAS category) covers airport capacity, traffic volume and non-extreme weather. "Usual" is the median of the same month in up to five earlier years, with 2020 left out; it appears once two earlier years exist.