After I wrote about how Delta Air Lines customer service agents came up with an idea that shaves a couple of minutes off turnaround time for the airline's jets at Hartsfield-Jackson Atlanta International Airport, I heard back from some other airlines. 

Actually, I was curious if they did the same thing as Delta, so I reached out to all of the Big Four. Southwest and United replied, while Delta also responded with a couple of other ideas worthy of attention. (Nary a word from American Airlines.)

Turnaround time is a big deal. The FAA reported in 2010 that flight delays cost the U.S. economy roughly $32.9 billion a year. Andit's one of the key metrics on which airlines  judge themeselves.

Here are some of the other things big airlines are doing to turn airplanes around more quickly.

45 degree pushback

This is the original idea that Delta customer service agents came up with. We'll summarize it here: Instead of pushing an airplane straight back from the gate, then turning it 90 degrees and pushing it again, the idea is to push straight back at a 45 degree angle.

This simple change shaves about a minute or more off turnaround time, which really adds up over 1,000 or more flights a day. Delta does it at Atlanta and Detroit. And, United tells me they do a 45-degree pushback at some airports as well, "depending on a variety of factors including aircraft type and setup of gate."

The Quick Turn Playbook

This one is all United. The airline has what it calls a "Quick Turn Playbook," which is a proprietary document that it says outlines "how all departments work together to help reduce the amount of time it takes to service and turn an aircraft."

"The playbook was developed with the help and input of United frontline employees," a United spokesperson told me. "We continue to go back to employees to solicit feedback on how it can be continuously improved."

Open seating

Yes, this one is limited to only one big airline--Southwest--and they were quick to point it out when I asked about turnaround tactics. Letting passengers take any open seat "saves us valuable time and keeps our aircraft moving efficiently," as a spokesperson put it.

It's hard to understand why other airlines don't copy this--perhaps not on entire plans, but maybe by letting economy passengers board in order of how expensive their fares are?

Anyway, for now Southwest is happy to have this advantage pretty much all to itself. As I wrote recently, Southwest CEO Gary Kelly made it clear the airline isn't going to change this policy anytime soon.

Self-parking guidance systems

Both Delta and United told me they use laser-guided parking systems at some airports and gates. 

Instead of an employee standing on the ground and guiding the plane in with a couple of orange flags or lights, the laser system lets the pilot know how to inch the plane up to the gate, and when to stop. That means the employees can get ready to hook airplanes up to ground power and do other tasks more quickly.

Not charging for checked bags

Again, this is just Southwest, which doesn't charge bag fees for any passengers. That's in contrast to economy class passengers on United, American and Delta.

As a result, on any given Southwest flight there are likely fewer people carrying bags onto the plane and trying to put them in an overhead compartment to avoid a bag fee. That means less blocking of the aisles, and a faster process. 

The one they're not doing

I found a few other interesting tactics. Ryanair, the low cost European carrier, says it cut turnaround time "dramatically" by removing seat back pockets, which means there's no place for passengers to stick trash that has to be cleaned out. 

But the interesting one is a more complicated boarding dance called the Steffen Method, after the astrophysicist who came up with it in 2014. In summary, passengers would board from the outside in: window, then middle, and then aisle. And they'd board from the back, skipping every other row.

One drawback: Travelers flying together couldn't board together if they were really strict about the process. Maybe that's why it hasn't really caught on.

An earlier version of this article appeared on my column on Inc.com.`