WASHINGTON, Nov 21 (Reuters) - The U.S. Federal Aviation

Administration warned major airlines on Friday of a "potentially

hazardous situation" when flying over Venezuela and urged them

to exercise caution.

The FAA notice cited the "worsening security situation and

heightened military activity in or around Venezuela" and said

threats could pose risks for aircraft at all altitudes.

There has been a massive American military buildup in the

region in recent months, including the U.S. Navy's largest

aircraft carrier, at least eight other warships, and F-35

aircraft.

The administration of U.S. President Donald Trump has bombed

boats allegedly carrying drugs that have departed from the

shoreline of Venezuela and other Latin American countries.

Direct flights by U.S. passenger or cargo carriers to

Venezuela have been suspended since 2019 but some U.S. airlines

fly over the country for some South American flights.

American Airlines ( AAL ) said on Friday it had stopped

overflying Venezuela in October. Delta Air Lines ( DAL ) said it

had stopped flying over Venezuela "a while ago." United Airlines

did not immediately comment.

The order requires U.S. airlines to provide the FAA with at

least 72 hours advance notice of planned flights but stopped

short of prohibiting flights over the country.

The FAA said since September there has been an increase in

Global Navigation Satellite System interference in Venezuela,

which in some cases caused lingering effects throughout a

flight, as well as "activity associated with increasing

Venezuela military readiness."

"Venezuela has conducted multiple military exercises and

directed the mass mobilization of thousands of military and

reserve forces," the FAA said, adding that at no point had

Venezuela expressed an intent to target civil aviation.

The agency said the Venezuelan military possessed advanced

fighter aircraft and multiple weapons systems capable of

reaching or exceeding civil aircraft operating altitudes, and

there was potential low-altitude risk from air defense systems

and anti-aircraft artillery.

The FAA said it will continue to monitor the risk

environment for U.S. civil aviation operating in the region.