It is chilling to think that two airliners were just one minute away from colliding over the Caribbean Thursday.

A Delta Air Lines flight and a Russian-registered passenger jet were flying toward each other north of Puerto Rico when cockpit alarms sounded. The pilot of the Russian plane — a Transaero Boeing 737 — acted swiftly, descending 200 to 300 feet.

The National Transportation Safety Board is investigating. The planes were both at 33,000 feet above open ocean and were "60 seconds apart from occupying the same airspace," said NTSB spokesman Peter Knudson.

Had one pilot not taken evasive action, the planes would have collided or just missed each other. The agency does not know which and is studying the matter.

The aircraft were about 180 miles north of San Juan when the near-collision happened at about 6:30 p.m. The Delta plane 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. Controllers at the Federal Aviation Administration's air traffic control center in San Juan told him the airliners were on intersecting flight paths.

The good news is that the cockpit alarms worked and a pilot reacted in a way that may have saved everyone on both planes. But how do such things happen?

That is for safety investigators to find out and explain to the public.