All UK airlines have been contacted by the UK's Civil Aviation Authority "to require them to review all relevant procedures" following the French Alps plane disaster.

This is what is known about UK airlines' policy of cockpit manning levels:

:: Virgin Atlantic - "We always ensure we have the highest safety standards and, while it is our common practice to have two members of our crew in the flight deck at all times, in light of recent events we are now in the process of formalising this to be policy."

:: EasyJet - From today it is changing its procedures which will mean that two crew members will be in the cockpit at all times.

:: Monarch - It has revised its flight-deck policy so that all passenger flights will require a member of cabin crew to stand in when the pilot or co-pilot leaves the cockpit for any reason.

The airline already practised an "eyes-on" check, where a cabin crew member enters the flight deck to check on the captain and first officer every 15 to 20 minutes.

:: Thomas Cook Airlines - It has changed its policy to ensure the cockpit is always occupied by two people.

:: Ryanair - Already required that two crew members be in the cockpit at all times.

:: Jet2 and Flybe - The two-in-at-all-times policy was also already in place with both carriers.

:: British Airways - The airline said it did not discuss "issues of security".