Old friends Boeing and Southwest are celebrating another milestone in their 40-year relationship after the airline's decision to launch the 737 Max.
However, as with many relationships that span decades, cracks have emerged since the foundations were laid when Southwest ordered 48 737-200s and subsequently launched the -300, -500 and -700 variants.
Before Southwest opted to remain with old faithful the carrier had, during the past couple of years, publicly voiced frustration over Boeing's inflexibility in granting delivery slots and the airframer's hesitancy in fully committing to re-engine the 737 during the past year.
In April, Southwest chief Gary Kelly declared that during his 25-year tenure at the carrier little time had been spent with any other airframer besides Boeing, and "that's got to be different in the future".
Even if Southwest never held court with other airframers, the carrier offered public praise for the Bombardier CSeries and revealed the Airbus A320neo was included in the technical evaluation conducted prior to the carrier settling on the Max.
Perhaps to make Southwest feel more appreciated and smooth over any ruffled feathers, Boeing opted to sweeten the Max deal. Typically dodging questions on actual pricing, Southwest said only that it received a substantial discount from the list price.
Now the cracks appear to be mended in what Boeing Commercial Aircraft chief Jim Albaugh labels a "truly special relationship" between the airframer and Southwest, the real work lies ahead. Southwest's launch customer status gives it a pre-eminent position in approving the final configuration of the Max.
In some ways, Southwest has a blank canvas in crafting the direction of Boeing's 737 Max development, since the airframer has yet to declare which variant - the -7, -8 or -9 - will be built first. Boeing intends to work with the carrier during the next five to six years to "make sure it is the right airplane for Southwest".
As it works to meets the airline's demands, perhaps Boeing should consider accelerating firm configuration from mid-2013, instead of trumpeting the fact it racked up more so-called commitments for the Max during the programme's first 100 days than rival Airbus did after launching the A320neo a year ago.
After all, the airframer has a big promise to keep, with Albaugh having told Southwest: "We'll deliver the real thing, I guarantee you, on schedule and on spec, and you will continue to have the best aircraft in this market place."
(Published as main leader in Flight International 20 December)