Who's the biggest planemaker on the planet? As I described yesterday, Boeing (NYSE: BA) recently reclaimed the title of most prolific plane seller in 2011, expanding its lead over archrival Airbus. But how long can it hold on to the crown?

This morning, reports began filtering out ahead of the Paris Air Show concerning a massive 200-plane sale that could reverse the balance of power. Indonesian airliner AirAsia says it may ink a deal to buy 150 to 200 Airbus A320neo aircraft at the show. If that happens, it will dwarf the would-be 150-plane order that United Continental (NYSE: UAL) didn't quite place in 2009 (UAL ultimately bought only 50 planes and deferred decision on the remaining 100). It would eclipse IndiGo's 180-A320 purchase of earlier this year. And at list prices, it could add as much as $18 billion to the revenue streams of either Airbus or Boeing.

Such a sale would also set the stage for yet another epic contest -- this time between United Technologies (NYSE: UTX), which has the most contracts for A320neo engines so far, and General Electric (NYSE: GE), which would like to grab more market share. AirAsia is reportedly considering both manufacturers for the engine work.

For Boeing shareholders, though, the main import of an AirAsia sale is that it could increase pressure to close more deals of its own. Already, Airbus has snagged a big 100-plane deal from AIG (NYSE: AIG) this year, and the biggest plane sale ever to IndiGo -- and now looks to land both the biggest and the second biggest with the AirAsia sale. Importantly, there's still a 200-plane contract from Ryanair (Nasdaq: RYAAY) to be won. If Boeing can win that one, it would parry Airbus' win in Paris and break its rival's winning streak.

My worry is that Boeing might panic and sacrifice profit margins in an attempt to win back the spotlight from Airbus. Remember: In contrast to the struggling and unprofitable 787 program, Boeing's 737s are still selling well -- so well, in fact, that Boeing has had to accelerate production three times in the past year and plan a fourth increase:

Here's hoping Boeing doesn't overreact to bad news in Paris this month. With hundreds of profitable birds already in hand, Boeing mustn't chase unprofitable contracts into the bush.

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