When was the last time you heard of an airline passing up an opportunity to jam more seats – and more people – onto its planes?

Don’t feel stupid. Nobody else can remember that happening, either.

But it’s happening now.

Delta Airlines doesn’t operate a lot of Boeing 777s; just 18 out of the 671 jets in its mainline fleet. But those 18 777s, in two different versions, WON’T be equipped with more seats as they all go through their scheduled interior updates between now and 2020.

In an extremely rare (these days) bow to passenger comfort Delta is choosing to keep its current nine-across seating in the coach class sections of its biggest international-range jets. Around the world most operators of 777s favor 10-across coach seating.

United, which has 91 777s in nine different configurations, recently made the decision to switch to 10-across economy class seating as those big jets go through the current round of interior updates

American, which has 67 copies of the 777 in six configurations, already equips most of its 777s with 10-across economy seating. And in the past few years, whenever it has had an opportunity to decide between adding seats or maintain exiting levels of seating comfort American has opted to stuff more seats into its planes. Most notably, American has ordered new Boeing 737-MAX 8 aircraft with two additional rows of economy seats, forcing it to reduce the distance between seats, called pitch, to just 30 inches. American plans to put two additional rows of seats on its older 737s when they come in for interior updates over the next few years.

Conversely, Delta is promoting – albeit not very aggressively – the fact that at 18.5 inches wide its 777 coach seats are the widest (and arguably most comfortable) in the industry, and will remain that way. United’s 777 economy seats all had been 18 inches wide (except for a few that had seats 18.3 inches wide).  Now, however, United is moving slowly to standardize its 777 economy seats at 17.1 inches wide. American’s 777’s have economy seats that range in width from a low of just 16.2 inches to a maximum of 18.1 inches.

Economy seat width and pitch appear on the surface to be minor details. But experience shows that customers care very much about how much – or how little – personal space they’ll have aboard commercial airliners.  But experience also shows that in most cases travelers keep on buying tickets  in ever-larger numbers even after airlines move to reduce one or both of those seating dimensions.

So it’s noteworthy that Delta is opting not to reduce economy passengers’ margins of comfort when it has a natural opportunity to pack more revenue-generating seats on its planes. In addition to offering seats that are 18.5 inches wide – some the wide bodied among us will appreciate greatly – Delta’s 777 economy seats will offer between 31 and 35 inches of leg room, depending on location within in the plane. That’s roughly in line with industry standards for wide body international flights.

Does this mean that airlines will now begin competing on the basis of comfort rather than price?

There’s hope. But don’t bet the farm on that concept taking hold across the industry.

Investors – and Wall Street analysts who, in effect, serve as investors’ mouthpieces – always want to see revenue growth. But after adjusting for year-over-year changes in capacity, it’s hard for airlines to show revenue growth because fare prices remain, by far, the biggest factor in consumers’ travel purchase decisions.  Adding seats generally allows airlines to bring in more revenue without having to raise their average fare prices by noticeable amounts.  Keeping the same number of seats makes it impossible for airlines to increase their revenue unless they raise their fares. But stiff competition, especially at the lower end of the price scale, keeps airlines from bumping up fares much, if at all.

In short, people keep on buying tickets to sit in cramped seats because they are price-sensitive; they just complain about it more. Seating comfort and space ranks well below price, schedule convenience and frequent flier program affiliation among the factors that influence consumers’ travel buying decisions.

Cynics also argue that airlines are adding seats in the back of their planes, and as a result are reducing hip, elbow, shoulder, knee and foot space for the passengers who sit back there as a way of twisting travelers’ arm to pay more – sometimes quite a bit more-  for so-called “Premium Economy” seats.  Premium economy seats, located in the front of coach sections, offer slightly wider seats and a couple of extra inches of leg room.  Typically those seats are bought by business travelers who aren’t paying for their travel out of their own pockets but whose corporate travel policies prohibit them from buying business or first class tickets.