Do not SAY
I lost my flight.
-Do SAY
I missed my flight.
To lose: is used to describe an object you cannot find.
I lost my keys.
To Miss: is used in the following context:
- Fail to get transportation
- Fail to take an opportunity
- Fail to attend an event
I missed the bus.
I missed the chance to meet you.
I missed the meeting at work.
