Those could be IFR holding patterns, but the length of the racetrack looks like it might be a refueling track.
Refueling and holding would be one altitude ... as the colors clearly show (you could also press K for the track labels) the altitude changes after one turn. Training tactical descents / approaches: https://globe.adsbexchange.com/?icao=43c208&lat=53.955&lon=-0.427&zoom=10.0&showTrace=2021-01-22 See the 12000 fpm descent rate. Click on the track to move the plane then check details on the left ... can also play it back after putting it in the right place.
I'd say you're spot on with the tactical approach training call-out. The vast majority of my track data analysis experience focused on flights which occurred in theater. As such, I've only observed a handful of these types of maneuvers over the past years where they executed the tight circular pattern with that same aggressive descent profile here. I've not seen what this shows and looks like to me as the use of military training routes (MTRs) as the infil/ exfil corridors. Either way, thank you for the vector check! I do want to address one of your points though. Refueling tracks are flown at a constant altitude, but to say that about holding patterns is not exactly accurate. While this isn't an example of what IFR holding patterns flight tracks, it's not accurate to say that aircraft in holding always maintain a constant altitude. It's most common along the arrival corridors which are acting as the transitional feeder routes as a means of maintaining required traffic separation during high volume arrival surges into major commercial airfields, and usually when the weather conditions are hard IFR causing cascade delays further up stream than usual. These 'holding stacks' consist of multiple aircraft holding on the same fix and side flying the the same holding patterns at a minimum of 1,000 foot intervals below FL290. The aircraft holding at the lowest altitude assigned, which is at or above the altitude normally used by ATC for arrival flows sequencing at the fix location, will hold until ATC is satisfied the aircraft ahead crosses a predetermined distance being used to ensure proper separation is maintained. Once this occurs, the controller will clear the bottom stacked aircraft to terminate the hold and proceed along the assigned route and altitude towards the next fix. Then, one by one, the controller clears each aircraft in the holding stack to descend and maintain 1000' while remaining established in hold, starting from the bottom up. Once the aircraft which was just cleared to terminate the hold reaches the same predetermined separation, they rinse and repeat. They look nothing like the tracks originally posted, I didn't look closely enough before I shot off my answer. I just wanted to make sure that folks reading this thread don't walk away with a misunderstanding of what flight track characteristics could be the results of a hold.
