Two airliners were one minute from colliding when one of the planes turned away from the other over the Caribbean last week, federal authorities said last Friday.

The National Transportation Safety Board (NTSB) said it was investigating an incident in which a Delta Air Lines flight and a Russian-registered passenger jet were heading towards each other last Thursday north of Puerto Rico when cockpit alarms went off.

The NTSB said the pilot of the Russian plane - a Transaero Boeing 747 - descended 200 feet to 300 feet to avoid Delta Flight 485. The planes were at the same altitude - 33,000 feet over open ocean - and were "60 seconds apart from occupying the same airspace," said NTSB spokesman Peter Knudson.

Knudson said the agency doesn't have enough information yet to know if the planes would have collided had evasive manoeuvres not been taken, or if they would have narrowly missed each other.

The two planes were about 180 miles north of San Juan when the near-collision occurred at about 6:30 p.m. EDT. The Delta Boeing 737 - with 152 passengers aboard - was headed from New York's Kennedy International Airport to Port-of-Spain, Trinidad.

"This was every bit the classic near miss," said Doug Church, a spokesman for the National Air Traffic Controllers Association.

Church said controllers in the Federal Aviation Administration's air traffic control centre in San Juan told him the airliners were on intersecting flight paths at the time of the incident.

The NTSB said there were no injuries.