In fact, it has become something of a running joke in the industry that the Government's delays in giving support to one option over the other have been a boon to the public affairs industry. The airports have been big spenders at party conferences in recent years, in addition to spending on agencies.
Expansion of one of London's airports has been a long-running saga, often frustrating business leaders. An Airports Commission was set up in September 2012, publishing its final report in July 2015, after which the then Secretary of State for Transport Sir Patrick McLoughlin announced that the Government accepted the case for airport expansion in December 2015. It was finally announced on Tuesday this week that Heathrow would be enlarged.
Both the statutory Register of Consultant Lobbyists, and the voluntary register run by public affairs membership body the APPC, reveal a number of the firms who have worked with both Heathrow - whose winning comms plan is seen as having had a better base of evidence - and its defeated rival Gatwick.
Just one firm is listed in the statutory register as a lobbyist working for Heathrow in the latest version of the register, for the third quarter of 2016; Portland. The same is true for all but one of the seven quarters since the statutory register was created - with the exception of Q2 2016, when it also worked with Stonehaven Campaigns.
Portland first lists Heathrow as a client on the APPC register in 2012. Previously, the APPC register shows, Blue Rubicon and later Open Road/Blue Rubicon (after the acquisition of Open Road in 2014), worked for Heathrow in 2011, then for a campaign known as 'Back Heathrow' in 2013, and again in 2015. The agency is now Teneo Blue Rubicon.
Green Issues Communique worked for Heathrow until 2013, the APPC register shows.
In mid-2015, Maitland starts listing 'Heathrow Hub', which later becomes 'Runway Innovations Ltd (Heathrow Hub)', as a client. Runway Innovations is an alternative plan to a third runway being built at Heathrow, under which an existing runway would be lengthened to increase capacity. A senior consultant of Maitland, Henk van Klaveren, now works for the Airport Operators Association.
The CIPR-operated UK Lobbying Register also shows Heathrow Hub as a client of Boscobel & Partners.
On the consumer side, The Red Consultancy was named on Heathrow's consumer roster alongside Cow and Hope&Glory in 2015. One Green Bean was added to that roster in August this year. Red had previously been appointed in 2011 to position Gatwick as "London's airport of choice".
Gatwick has most recently been working with Edelman, Hanover and London Communications Agency, the latest statutory register shows.
The APPC register shows PPS Group and Quiller Consultants also working with Gatwick - the latter only beginning work with the airport earlier this year, while PPS lists Gatwick as a client going back to 2014.
Grayling was appointed as Gatwick's comms partner for a two-year period beginning in December 2014, but is no longer working with the airport. Brands2Life then succeeded Grayling in September the following year.
In addition, the APPC register shows that Gatwick worked with Fishburn (previously Fishburn Hedges) from 2012 until 2016, after it merged to become FleishmanHillard Fishburn in November 2015, and with Instinctif for a similar time period.
Finsbury previously worked with BAA - the company which operated UK airports including Heathrow and Gatwick, before being renamed in 2012, when MHP was appointed to handle financial PR for Heathrow. MHP held this role until 2014. BAA also took on Mischief on a 12-month consumer, trade and corporate PR brief covering Heathrow in 2009.
Cogitamus has worked with the protest group Heathrow Association for the Control of Aircraft Noise.
The statutory register also shows PLMR working for London City Airport and Lansons for London Luton Airport this year, and Westbourne Communications having worked with Birmingham Airport in 2015. In addition to these, Cardiff Airport is working with the agency Deryn, the APPC register shows.
One consistent factor in recent years at Heathrow has been Clare Harbord, the airport's corporate affairs director since July 2011. Heathrow's in-house comms team is led by director of external affairs Nigel Milton.