Virgin Atlantic

The move could see shares offered to private investors as well as big City firms, but mean he loses overall control of his flagship business.

Virgin Group owns 51% of the airline, and US-based Delta Air Lines the rest.

It is understood Virgin has hired City advisors to draw up flotation plans, but the airline called it speculation.

The Unite union said legal notice has been served in 51 cases, the majority of which are against British Airways.

EasyJet, Thomas Cook, Jet2 and Virgin Atlantic are also subject to the legal action over "aerotoxic syndrome".

The airlines said that previous studies found no proof of long-term ill-health arising from cabin air quality.

The Unite union, which represents airline staff, claims pilots and crew are exposed to frequent "fume events" when air drawn into the aircraft becomes contaminated by toxic compounds.