Turkish Airlines' commitment to order 75 Boeing 737 Max aircraft brings to four the number of airlines that have plumped for both Max and Airbus A320neo aircraft.
But as Ankara's flag carrier joins American Airlines, Lion Air and Norwegian in this category, a question arises: why are some prepared to miss out on the much-vaunted benefits of fleet commonality, which simplifies maintenance and pilot training?
One of the factors driving airlines towards a mix of Max and Neo is near-term slot availability. "It may be your only choice to go to both manufacturers to get slots to sustain your expansion," says Chris Seymour, head of market analysis at Flightglobal's Ascend consultancy arm.
"Given the recent numbers of orders for both families, that's probably a bit understandable." The Ascend Online Fleets database puts the number of A320neo-family orders at 2,061, while the Max figure is 1,185.
At the time of its decision to split a 460-aircraft order between Airbus and Boeing - opting for 100 737 Max and 100 A320-family aircraft therein - American Airlines said that no single manufacturer could "provide the number and variety of aircraft" required to entirely replace the carrier's narrowbody fleet.
Likewise, Norwegian cited a goal of ensuring capacity, as well as encouraging competition, when it committed to 100 Max aircraft and 100 Neos. And after Lion Air followed an order for 201 Max aircraft with one for 174 Neos, chief Rusdi Kirana said: "Since we need more aircraft, we have to go to two manufacturers. We need to accelerate delivery of the aircraft."
Yet a mix of the two types may also be a means to optimise network planning. "The families do have slightly different payload/range capabilities," observes Seymour. For example, Airbus is pursuing a 236-seat A321neo configuration. The largest Max is the 180-seat Max 9 (which can carry 215 passengers if a single rather than two-class configuration is used). Turkish's letter of intent to take Neo aircraft covers 53 A321neos; from Boeing, it intends to take 65 of the 162-seat Max 8 variant, and 10 Max 9s. "Depending on your route network, you can use both families for differing missions," argues Seymour. "Allied to that you can have subfleets for different operations." As a case in point, Garuda is a 737 operator, but its low-cost subsidiary Citilink has ordered Neos.
Some of the drawbacks of a diverse fleet have arguably been mitigated by the rising popularity of sale-and-leaseback arrangements, which allow airlines to free themselves of the burden of having, eventually, to remarket the aircraft. The other factor clearly at play is the positive outcome that can come from pitting two fierce rivals against each other. "I think the advantages of fleet commonality might just be outweighed by the advantages of competitive pricing," says Teal Group analyst Richard Aboulafia, who also notes that "completely divergent propulsion philosophies" underpinning the Max and Neo offer an argument for "hedging your bets against risk". He adds: "You're also potentially taking advantage of one family that does certain types of routes better than the other: 737 Max better for shorter and A320neo for longer range."
Aboulafia offers a characteristically pithy take on the narrowbody battle between engine manufacturers Pratt & Whitney and CFM International, which compete within the Neo programme, although the latter is sole-source supplier to the Max. "It could be that they're just two paths to get to the same goal," he says. "Or it could be that - to quote Mark Knopfler of Dire Straits - 'Two men say they're Jesus, one of them must be wrong'."
Turkish's fleet decision, meanwhile, can be viewed through the prism of the airline's particular circumstances. "Geographically their position isn't all that different from the Arab Gulf carriers, and yet they've got excellent O&D traffic, which, aside from South India traffic, the Gulf carriers don't have," says Aboulafia. "They might have a strong growth story to tell for some time here."