It means the outbound travel is already taken.
"Partially flown" typically refers to a situation where some, but not all, of a scheduled flight has been completed. This could occur due to delays, diversions, or other reasons that prevent the flight from proceeding as originally planned.
that someone might have died
it was flown in 2014
I/You/We/They have flown. He/She/It has flown.
1912 was when the first helicopter flown
This means that: he never thought that the bird could have left it's nest.
descended? Driven (in a car, as opposed to flown in a plane). Walked (as opposed to having flown somewhere.)
It is flown in reverse to signal distress.
Bird Has Flown was created in 1969.
The Eagle Has Flown was created in 1991.
1912 was when the first helicopter flown
Flown is the past participle of fly.
The past tense form is flew. Flown is the past participle. fly - flew - flown