Air travel is stressful for many people, and not just because of fear of flying. More and more flights seem overcrowded — even when they’re not actually overbooked — with less elbow room and legroom and additional fees and surcharges.

Regardless of whether you’re being pampered in first class or sandwiched between two sumo wrestlers in economy, you arrive at the same time as every other passenger on your plane. Delays are the great equalizer.

Different airlines have very different track records when it comes to delays, and that can be a major consideration for travelers with tight connections or important meetings. Based on a review of flight data compiled by FlightStats, which tracks monthly flight data. 24/7 Wall St. has identified the airlines with the most and least delays.

Click here to see the airlines that are constantly delayed.
Click here to see the airlines with the fewest delays.

Not surprisingly, several of the worst offenders are also discount airlines, like the American airline JetBlue or Britain’s EasyJet. Canada’s low-cost carrier WestJet, however, has managed to maintain a good track record.

Of course, punctuality isn’t everything: Brazil’s LATAM Airlines ranks among the most on-time airlines but also among the least safe. So the next time you book a flight, in addition to safety, cost, and convenience, you may also want to consider an airline’s on-time performance record.

To identify the airlines with the best and worst on-time track record, 24/7 Wall St. reviewed flight data collected by FlightStats. Airlines are ranked based on the share of total flights in July 2017 that missed their planned arrival time by at least 15 minutes. To count among the airlines with the most delays, at least one-third of an airline’s flights must have been delayed in July. To make the list of the airlines with the fewest delays, less than 20% of flights for July had to be delayed. FlightStats only considers airlines for which at least 65% of monthly flights are tracked.