Check in Time

Supposedly, checking in as early as possible reduces the risk of being bumped if the flight is oversold.

Can’t answer why the app says 6 days.

Some airlines let you check in earlier than 24 hours.

Most airlines also have a check in cutoff time. If you have not checked in by then, reserved seat or not, you will miss your flight. Delta international cuts off check-ins 60 minutes before the flight.

Checking in online saves time at the airport. Why would you want to wait in a possibly long line when you can do it in the comfort of home.

Online check-in for an international flight on Delta is usually 24 hours ahead of time. So it's not by days but by hours. The fact that the app says 6 days may just mean an approximation close to that 24 hours mark.

The point of checking in is to let the airline know you will be there to take your seat. It also gives you a boarding pass so you can get through security at the airport without having the bother of stopping at an agent's desk or a kiosk. Also, if you are running late and you get to the airport late, if you haven't checked in, the airline may give your seat to a standby passenger. That doesn't mean you would be bumped from the flight, but you might not get your original seat.

I would never not check-in early, especially for an international flight.

On Monday you'll start seeing your check-in time counting down in hours. That's when you know you're really close 🙂
I usually check in the minute I can, which is 24 hours before my flight (Delta).

With Delta, check in begins 24 hours before the flight departs. Airports are chaotic so why would anyone want to wait when one can check in online and get the boarding pass on the Delta app? As has been mentioned above, airlines oversell, so it is best to check in as soon as one can. It’s not over yet though. Don’t wait to arrive at the gate until 15 minutes before the flight departs because the door to the aircraft could already be closed.

All of the above. And, if you'll be checking luggage instead of carrying it on board, you can use a "bag drop" line at the airport instead of waiting in the check-in line. That will also save you time. Some airlines let you print luggage tags as part of the online check-in process, but I don't know if Delta is one of them.

Online check-in is one of the few noticeable improvements in air travel in recent decades. Celebrate it!

“ Delta international cuts off check-ins 60 minutes before the flight.”

I was on a work trip international flight that my director was also flying. I had my favorite bulkhead seat with extra leg room in Comfort Plus. I was planning on giving him my seat when he boarded, if he had an aisle seat, because he’s very tall and large. Well, I never saw him board….because he hadn’t checked in ahead of time and missed this 60-minute cut-off time.

Another good reason for checking in ASAP is that it gives you an early indication of known problems. If there was a last minute cancellation, you aren’t finding out about it at the airport. There can be a several hour lag between cancellations and email notifications to passengers.

As stated above. On Delta the app will say 6 days when the check in time is 6 days and 23 hours.
Bugs me too.

With some airlines, an online checkin 24 hours before also may give you the opportunity to pick a different or better seat.
As someone else said, if you are checked in early, less chance of being bumped.

I print my boarding passes 24 hours ahead, but I also save them on my phone and IPad.
I have needed proof after the fact when flights, times, delays etc have occurred, in order to make a claim.

Because the airline is actually counting it in hours and days, so if you are six days23 hours and 59 seconds from checkin - it’s six days.

And no, for most airlines, checking in at 24 hours does not increase your chances of an upgrade, nor decrease your chances of being bumped. Your chances for upgrade are based on a lot of components, and even if check in time is on the list it’s so far down it’s never a factor. Bumping is something they try not to do and probably your biggest two factors are going to be your fare class and your status, if any, with the airline. If you’re on a really cheap fare and its oversold, you probably have the biggest risk of getting bumped , but that said, every airline I’ve ever been on has gone to extraordinary lengths to avoid that. I was just on a flight to California where they gave away almost $1000 to get somebody to get off. (Unfortunately I was going for a work meeting so I couldn’t get off. And I checked in on the way to the airport in the Uber. So I was pretty late on the check-in list, but I was never at risk of being bumped.)