Hello there Roey M.,
Thanks for posting here on the Apple Support Communities! This is a place where other Apple users can submit questions or respond to others to help lend a hand. Let's take a closer look as we do our best to provide some additional insight.
To get started, does this only happen with the events from these flight reservations, or does it happen with other apps or from other services as well?
Otherwise, we really would not be able to speculate other than referring you to who ever you booked with. In the meantime, you may want to manually add events to ensure their accuracy and make sure you don't miss a flight: Create and edit events in Calendar on iPhone
We hope this helps get you pointed in the right direction.
Take care.