Budget airline Easyjet has said it will require two crew members to be in the cockpit of its aircraft at all times.
The change, effective from Friday, comes after UK airlines were told to review procedures following Tuesday’s Alps crash in which 150 people died.
The Civil Aviation Authority (CAA) said in a statement they will “continue to monitor the situation” as the crash investigation develops.
Meanwhile, Air Canada and Norwegian Air Shuttle have announced similar plans.
The CAA said it has told all UK operators to review procedures.
All UK airline pilots undergo extensive and regular medical assessments to determine their fitness to hold a licence, it said.
Examiners are required to assess a commercial pilot’s mental health at each medical examination.
Marseille prosecutor Brice Robin said earlier the co-pilot, named as Andreas Lubitz, was alone in the cockpit of the Germanwings plane when it crashed in the French Alps.
The co-pilot intentionally started a descent while the pilot was locked out, he said.
Mr Robin, citing information from the “black box” voice recorder said there was “absolute silence in the cockpit” as the pilot fought to re-enter it.
The Airbus 320 from Barcelona to Dusseldorf hit a mountain, killing all 144 passengers and six crew, after an eight-minute descent.
Among those killed were Britons Paul Bramley, 28, from Hull, and Martyn Matthews, 50, from Wolverhampton.
Seven-month-old Julian Pracz-Bandres and his Spanish-born mother Marina Bandres Lopez-Belio, from Manchester, also lost their lives, the Foreign Office said on Wednesday.
The second “black box” – that records flight data – has still not been found as a massive recovery operation continues.
The British Air Accidents Investigation Branch (AAIB) confirmed it has a “black box” expert working with French investigators who has been there since Wednesday.