There is something about single aisle jets like the one that splashed down on New York’s Hudson River today that you are never told in safety briefings on any airline.

And that is that if you were to pop the rear exits in a “water parking” incident like today’s, the jet will sink — very, very quickly.

Airbus A320s, like the one involved in today’s dramatic but fatality-free crash, and their Boeing 737 counterparts, will come to rest in survivable ditchings in a tail down attitude with the rear door sills under water.

But airlines all around the world consider this “too much information”. Instead passengers are asked to study “the safety card in front of you”, which gives easy to follow instructions, also reproduced in large letters and symbols on the inside of the doors, as to how to release the doors if the cabin attendants are “incapacitated”.

Bear this in mind. You are asked to note your nearest exit. And you are shown how to operate it. But you are never told not to deploy the rear doors if you find yourself on a body of water like Port Phillip, or Botany Bay, or the mouth of the Brisbane River.

A US Airways Airbus A320. Notice the rear doors near the tail

The Airbus A320 after landing. The rear doors are now submerged.

In today’s outstandingly successful emergency landing on the Hudson River, the crew seated in the jump seats beside each rear door had been trained to urge passengers forward to the overwing and front sets of exits in such a situation.

This was exceptionally important in New York today. Not only was the river freezing cold, but fast flowing. The jet floated from around 50th Street on Manhattan to at least 23rd Street in a matter of minutes, bedecked on the wings, and the forward door slides, with passengers looking as if they were waiting for a train.

The forward slides on which most of them were standing could also have been detached and turned into life boats.

Awareness of the dangers of the rear exits in a ditching is just one of the critical elements of cabin crew training at Qantas, Jetstar and Virgin Blue.

But what if the rear section cabin crew were incapacitated?

Maybe a sign DO NOT OPEN AFTER A WATER LANDING should be affixed to the inside of the rear doors. CASA and the airlines have been asked for their views on this.

The flight path from take-off to crash landing. Courtesy of Aviation Herald

Early reports are that the US Airways flight struck geese soon after takeoff. However, the height above ground and the momentum of the jet seems to come together fortuitously, because live flight tracking sites showed it reached a height of about 3000 feet, and remained airborne for around six minutes before splashdown.

(These figures are unofficial.)

After crossing a tract of suburbs and electing not to land at the small Teterboro field which they were fast approaching, the pilots glided the plane down the Hudson River, clearing the George Washington Bridge and its 180 metre tall pylons before splash down.

Bird strikes causing passenger flight crashes are rare. The last significant accident was 48 years ago, on 4 October 1960, when an Eastern Air Lines Electra turbo prop hit seagulls on taking off at Boston’s Logan Airport and crashed with the loss of 62 lives out of 72 people on board.