Do you know how this can happen?
Generally speaking should say the wind be calm, you're cruising at FL400 in your 77W. You're 200nm to run and have been asked to lose 10 mins. I'd imagine you're pretty close to min speed already at FL400. My question is would you rather stay at that altitude and speed and take a lap of the pattern, or descend lower to reduce the TAS and maybe take what you can 't lose with a vector. Technically speaking what would be more efficient. As soon as you've been assigned a delay you're now flying for best endurance instead of range. Is the best endurance going to be at mid levels as opposed to way up high? Or is it more efficient to stay high?
As a side note I was amazed on my last famil flight which was on an A388 from Auckland to Brisbane. Cruising at FL4XX at what was probably M.84 or so and 260 odd indicated or whatever it was and were assigned a delay of 15 minutes. I was very impressed at how slow the A388 can actually fly, we slowed down to about 210kts IAS and started a gradual descent for next 100nm or so. Still needed a lap of the pattern but it surprised me how flexible that aircraft is.