Bosses at the networks are thought to be personally involved in the global pitch, including WPP's Sir Martin Sorrell, whose presence was key in winning the high-profile HSBC account last year.
Etihad, the national airline of the United Arab Emirates and based in Abu Dhabi, is not such a high-profile client as yet, but is massively expanding its marketing services operation.
The airline bought 24 aeroplanes last July, including four of the headline-hitting A380s – Airbus' huge new double-decker aircraft.
Like the HSBC brief, the pitch involves the whole spectrum of marketing services, from creative and media advertising to PR.
One agency boss involved in this latest pitch said: "Massive global pitches like this are very much the future and we are seeing people right at the very top of the networks getting involved in a bid to win this sort of business."
Another agency head said: "Someone like Sorrell is obviously a valuable new business weapon."
Pitches and the lengthy procurement process for the Etihad account started back in December and an announcement of the winner is said to be imminent.
A spokesman for the airline said: "The decision on our advertising partners will be announced in the very near future. We are at the tendering stage at the moment."
WPP will be many people's favourites going into the process after a string of global and pan-European account wins of late, including Unilever, Nestlé, Samsung and HSBC last year.
For the HSBC pitch early last year, Sorrell was one of the agency networks chiefs who personally pitched for the business.
However, WPP's flagship media agency MindShare will not be part of the airline pitch as it already holds the account for German airline Lufthansa. It is unclear which agencies Omnicom and Publicis would use if successful.