The appointment follows an initial four-week brief in September, secured by APCO after a competitive pitch in advance of the TUC and Labour Party conferences.
The Prime Minister's former special adviser Darren Murphy, now an APCO director, leads the account.
Gate Gourmet workers voted to accept a deal to end the dispute at Heathrow Airport at the end of September. The deal with the Transport and General Workers' Union involves hundreds of voluntary redundancies. Management has insisted the cuts are necessary to avoid administration.
On the back of the agreement, Gate Gourmet last month signed a new deal with British Airways.
'Our brief is to communicate the message that this company has returned to a state of corporate normality,' said APCO UK managing director Simon Miller.
Parent firm Texas Pacific Group continues to use Gavin Anderson for more reactive media enquiries about Gate Gourmet. GA was brought in as the summer dispute flared up.
The row broke out on 10 August when Gate Gourmet sacked 670 staff after they walked out in protest at its restructure plans. A day later BA baggage handlers and loaders joined them in sympathy, leaving BA flights from Heathrow grounded.
The case triggered calls from the TUC to allow secondary industrial action, a notorious feature of the 1970s that was outlawed by Margaret Thatcher's government.
Miller said: 'It is important for government to know there is a lid on all this.'