Budgetary pressures have influenced nations around the world over the last year in how they operate their existing military aircraft and seek to acquire more capable and cost-effective replacements.
While some have chosen to defer their replacement decisions, others have taken more drastic action, by wielding the spending axe on what had previously been viewed as essential assets.
The highest-profile examples have come in the UK, with the early retirement of the nation's BAE Systems Harrier GR9 ground-attack aircraft and the cancellation of the long-delayed BAE Nimrod MRA4 project. The latter decision leaves the Royal Air Force with no dedicated maritime patrol aircraft - a dramatic choice for a nation at the top table of NATO.
The UK's funding crisis has led to the withdrawal of its Harrier GR9 strike aircraft. Picture: Abbie Gedd, Royal Navy
Elsewhere, the cost and complexity of operating aged equipment has seen several other types leave use. Most recently, the Royal Australian Air Force stood down the world's last General Dynamics
F-111s, with their duties assumed by its now-operational Boeing F/A-18F Super Hornets
Australia will have received all 24 of its new type by October 2011, as it moves closer to firming up an expected 100-aircraft commitment to Lockheed Martin's F-35A Joint Strike Fighter. Despite a tough year, the US-led programme remains the dominant force in the long-term combat aircraft sector, and accounts for over 3,000 of the 6,700-plus pending orders listed here.
In total, this year's World Air Forces directory includes almost 54,000 military aircraft in the active inventories of 161 nations, plus confirmed orders for over 5,200 more. Combat aircraft account for 33% of the current total, just a fraction below the 34% stake for combat helicopters. The remainder is divided between training aircraft and helicopters (20%), transport aircraft and tankers (10%) and special mission aircraft (3%). As expected, the US armed forces have the largest number of aircraft in all categories.
The directory has more than 4,000 fewer aircraft listed than 12 months ago, with this reduction in part due to improved data with regard to the operational status of Soviet-era types. Also excluded are almost 900 aircraft listed by Flightglobal's MiliCAS and HeliCAS databases as being dedicated to VIP transport tasks.
For nations around the world, replacing obsolete equipment is both an operational and an industrial imperative. India is looking to work with Russia on a development of the latter's PAK-FA, one of the most exciting types to have achieved flight status during 2010. An agreement on their proposed joint fifth-generation fighter aircraft could come soon. The coming months could also provide developments in the Indian air force's medium multi-role combat aircraft competition, and also on a possible deal with Boeing for 10 C-17 strategic transports.
The promise of meaningful workshare and technology transfer for local companies will remain a key driver in future type selections in many countries. Embraer enjoyed a remarkable run in 2010 linked to its KC-390 tanker/transport, being developed for an initially 28-aircraft Brazilian air force requirement. If its design proves a success, at least 32 more could be ordered for prospective partners Argentina, Chile, Colombia, the Czech Republic and Portugal.
As the battle for international orders becomes harder fought, these factors are likely to become ever more important.