Another thing I do not understand

Last night I went to the airport in Mexico City with a friend who was going to meet the Cardinal who was coming from Monterey.  His flight was delayed.  The flight was originally scheduled to land at 7 PM.  But by 7:58 the flight board had the following message regarding Aeromexico 931 from Monterey - A Tiempo (on time).  All of the other flights on the screen had landed but there it was 58 minutes late - and still expected to be on time.

The photo is from my phone and I took it in a hurry - but you get the idea.