Frequent fliers know that it usually takes less than an hour to get to San Francisco from Los Angeles.

But many non-stop flight schedules from various airlines report travel times up to 90 minutes or more.

Travelers aren’t going crazy. According to a new study OAG Aviation Worldwide, airlines around the world have been padding flight schedules for almost two decades so executives can boast about improved on-time performance rates, reports the Los Angeles Times.

In Sept., the Department of Transportation reported that 78.1 percent of flights on the country’s leading airlines arrived on time in July—which was up from 74.8 percent the previous month and 75.6 percent in July 2014.

But according to OAG’s study, those figures may only reflect the fact that airlines were adding extra minutes to the same flight paths year over year.

In one example from the study, OAG examined over 1,400 flights scheduled between Los Angeles International Airport (LAX)and San Francisco International Airport (SFO) in 1996 and found that no flight took longer than 90 minutes.

But in 2015, almost half of the flights scheduled between the two west coast hubs allotted between 90 and 110 minutes, according to the study. Overall, airline flight schedules between LAX and SFO increased 8 percent.

In addition to allowing carriers to post better on-time rates, the study suggests that airlines have also boosted time allotted for flights to deal with increasing tarmac congestion at various airports around the world.

“At airports which are congested, airlines need to keep schedules realistic so their timetables are reliable,” the study said.

A spokesman for a airline trade group Airlines for America dismissed the idea that carriers are simply inflating schedules to improve on-time rates.

Said spokesman Vaughn Jennings,  “We have the same goals as our customers, which is to get them, their luggage and packages to their destination safely and on time.”