The presence of obstacles to which aircrew are not notified.

The presence of obstacles in the vicinity of an aerodrome that have not been published in an AIP or NOTAM'ed. This might include disabled aircraft, temporary construction at an aerodrome, or building works in the vicinity of an aerodrome.

If operators and their flight crew are not aware of the obstacles, obstacle clearance during landing or departure may be compromised, with a risk of obstacle collision.