Will I need a 2 prong adapter to use my headphones on the airplane?

I usually fly Delta, and I have not had to use a 2 prong adapter for a long time. For international flights, they will give you earbuds, earplugs, and eye mask in economy. Of course, the ear buds are not high quality! I always take my own, but if I forget them, I know that I will still be able to watch the movies.

Never seen a 2 prong headphone outlet. I have heard they exist, but they must be pretty rare - every flight I have been on, on multiple airlines, uses standard headphones. The flight attendants always hand out earbuds, but I prefer mine and have never had trouble using them. However, if you were somehow on the mythical 2-prong outlet plane, appropriate headphones would be provided.

Depends on the airline and the plane you end up on.

Continental/United was the last airline I know of that had special plugs. They then forced you to buy their headphones.

Standard plugs work fine these days. The airlines then just expect you to buy their TV content.

I have flown several different airlines. I bring my own headphones and it has always been a single plug.

I remember the two plug proprietary headphones. When I had them they were not electronic but rather hollow tubes which sent the sound up from the armrest. The were awful, they leaked badly, they just conveyed the sound enough to watch the movie on the big screen if people weren't in the way. British Airways, or maybe BOAC, I forget the years.

Probably not, but I always bring it just in case. It is so small.

I think that I’ve used it once in the last 10 years (and I don’t remember which airline it was on.

The Air France plane we had on our flight from CDG to MSP in 2016 had the 2 prong headphone plugs. It even still had ashtrays in the armrests! The earbuds they handed out were 2 prong, of course, but if you wanted to use your own (like my husband did) you needed the adapter. We traveled to Europe again in 2017 on AA and 2018 on Delta and both planes were single prong.

British Airways my last two flights had two prong headphones. I used theirs when I wanted IFE, and my own when I used my mini ipad

Thanks for all the helpful follow up.