I'm original DL and have flown the 757/767 and the MD88 so I can't speak for what's on the former NWA planes, but the vast majority of pilot I fly with, including myself, wear the Telex 750 with both earpieces. The company headsets are single sided, green DC clamps. 'Nugh said.

Here are some things to keep in mind:

-DL planes don't have hot intercoms. I wish they did, but I guess they didn't spring for that option. With that said, the 75/76 cockpit and especially the MD88 is quiet enough where you don't really need it. Most of the time, I'll slide the earpiece behind my left ear (I'm an FO) and often, I'll just take the whole thing off above FL180.

-I've never flown the 737 but I'm told is nosier. From the times I've jumpseated on them, it seems most guys have sprung for the Telex 850s.

-Unlike a regional jet, especially an EMB-145, you're not wearing a headset for hearing protection. The cockpits are too quiet for that. Likewise, you don't want to wear DCs, because without a hot intercom, you won't hear what the Captain is saying.

-I'd go with the Telex 750. They're light weight, fit easily in a flight kit and you can find them on ebay for around $75. Although nice, the 850s are bigger, more expensive and for what you'll be flying as a new hire, not necessary. Once you're off first-year pay and have a better feel for things, then you can consider them or any other option.