Steel left the corporation last month to launch his own PR practice, which will include work for the BBC.
He will work with Johnston Associates to support the growing reputation management and crisis comms practice at the firm and to help business development.
Steel said: ‘Johnston Associates is the pre-eminent aviation public relations company in the UK and represents global brands. My relationship with Johnston Associates will complement my work with clients in the UK and abroad.’
Johnston Associates was founded in 1998 by MD Kevin Johnston, who previously managed communications for BAA’s Terminal 5 project.
Johnston said: ‘Donald has a wealth of strategic media relations and crisis management experience and a network of business relationships that span the globe.
‘His unique mix of strategic and front line media relations experience, combined with a growing profile in many parts of the world, will enable him to play a key role in the growth of Johnston Associates.’