[Ruy Dias de Bivar]

Sounds like a probe looking for a weakness or lax in security.

Possibly “dry run” for a future attack.

[Raycpa]

Could have been a decoy to get the spotlight off of another passenger.

[Ben Hecks]

Possibly “dry run” for a future attack.

We don't know, of course, how many other dry runs went undetected.