Maitland is reporting to corporate affairs director Jane Johnston and has appointed Julie Harris to lead the account.
Fleishman-Hillard, which repitched, had worked on the business since 2006.
The Government holds a 49 per cent stake in NATS and a golden share, which usually gives power of veto over other shareholders in certain circumstances. Last year it announced plans to sell but changed its mind in July.
The company’s other shareholders include a consortium of seven airlines, which holds 42 per cent; NATS staff, who hold five per cent, and Heathrow Airport Holdings, which holds four per cent.