Three C-17s just left Ramstein Air Base headed east about five minutes apart.

[mahatmakanejeeves]

https://globe.adsbexchange.com/

Hex ID Callsign Type Alt. (ft) Spd. (kt) Wind D. Wind (kt)
ae07f5 United States RCH223 C17 ▲18425 384
ae1179 United States RCH215 C17 ▲21975 398 72° 24
ae2fae United States RCH1831 C17 ▲12150 338 41° 13

[dem4decades]

1. I take it they're personal transport?

[LearnedHand]

2. Seeing 4, one headed for Ramstein

Edit: Stupid trivia, but the tricked out plane used in later agents of shield seasons was based on the C-17.

[ProudMNDemocrat]

3. The C class are Cargo.

They do carry passengers as well, along with heavy cargo.

I have flown on C-17 Globemasters. They are monsters.

While in Hawaii, one flew over my son's place
The house shook. It was on final approach to Hickam AFB.

[unc70]

4. Lots of C-17s out there almost all the time

Those planes are almost always on the move carrying military freight (and personnel) around the world. For example, from North American bases to Europe and then on to the Middle East.