The number of recent helicopter incidents is a "matter for concern" following the Glasgow pub crash, says the British Airline Pilots' Association.
The group extended its sympathy to everyone involved in the crash, which saw a police helicopter smash into the roof of The Clutha Vaults pub on Friday night.
At least eight people died and 14 were seriously injured in the incident, Sky sources say.
Investigators are trying to work out what caused the aircraft to fall from the sky into the crowded bar.
But BALPA warned about speculating on the cause of the incident before the full facts are heard.
"Whilst there will be understandable questions on why this happened, it is our experience that speculation about causes is often wide of the mark," BALPA said.
"Nevertheless, trends in helicopter safety is a matter of concern after a number of recent incidents including those in the North Sea.
"We hope that ongoing inquiries by the Civil Aviation Authority and the House of Commons Transport Select Committee into helicopter safety will also have the opportunity to look into the circumstances around last night's incident too."
At least one aviation safety expert believes something "dramatic" suddenly occurred to cause the police helicopter crash.
The pilot would have had either little or no control of his aircraft in the final moments of the flight, Flight Global's operations and safety editor David Learmount told Sky News.
But he added that although a witness has described the helicopter as dropping like a stone, there were indications that the pilot might have still had "some ability to fly" before the impact.
He said: "This type of helicopter is sophisticated and robust. It's a very modern aircraft. I think what has happened here is that you have had an aircraft that became either uncontrollable or partially controllable.
"We just don't know how much control the pilot did have in the final seconds of the flight. Something dramatic has probably suddenly occurred - probably some mechanical failure of some kind."
Mr Learmount said he thought that if the helicopter had been completely uncontrollable then the crash could have been "even worse".
The twin-engined Eurocopter EC135 T2 which came down on the pub is the third involving police helicopters in the west of Scotland.
In 1990, Sergeant Malcolm Herd died when a Bell Jet 206 helicopter crashed in bad weather at Eastwood Toll, Newton Mearns, Glasgow.
The 32-year-old father-of-four was in the former Strathclyde Police force helicopter when it struck the side of a block of pensioner's flats and fell to the ground.
Twelve years later in February 2002 another police helicopter crashed in a field 150 yards from Upper Wellwood Farm, near the village of Muirkirk, East Ayrshire.
The three men on board - Constable Kenneth Irvine, 35, Constable Neil McIntosh, 40, and civilian pilot Alfonso Gasparro, 31 - had what witnesses described as a "miraculous" escape.
The Eurocopter EC135 T2 is of a family of aircraft that first entered service in 1996. More than 1,000 have so far been manufactured.
The T2 is a replacement for the T1 and went into production in August 2002. They are widely used by police and ambulance services and for executive transport.
In September 2007 a Eurocopter EC135 T2 crashed east of North Weald Airfield in Essex. Although the pilot and his wife were unhurt the aircraft was badly damaged.
An AAIB report into the incident said there had been a disengagement of the autotrim - used to maintain the aircraft's position.
This had led the pilot to think he had suffered a total engine failure. He positioned the helicopter for a power-off landing in a suitable field but part of the tail of the aircraft struck the ground and the aircraft rolled on to its side.
The AAIB recommended Eurocopter review the Stability Augmentation System (SAS) switch system on EC135 helicopters "to reduce the likelihood of inadvertent de-activation of the SAS".
Story, video and comments/reaction: http://news.sky.com
A Police Eurocopter EC135 similar to the one that crashed in Glasgow
Eurocopter EC135 T2+, G-SPAO, Bond Air Services Limited for Police Scotland: Accident occurred November 29, 2013 at The Clutha Pub, Stockwell Street, Glasgow, UK
