The B787-family cruises typically at M0.85, but the economical speed, which is basically to save a little bit of time and fuel too then M0.87 is used. When Which Airline and What Reasons are behind for a 787 to fly at .87 is unknown to me, as that can depend on various factors from weather to delayed flight to airline operations.
But the B787 does not fly any slower than .85 as that speed is what you’re supposed to aim at and fly at basically every time though 0.87 is not wrong, but I don’t know in which situations a pilot would choose to fly that little but faster.
Source: DeerCrusher! 🦌
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But still, even if you flying at .87, a certain altitude, with a certain load factor, you will still stall, thats’s this earth’s physics for you ;)
The one in the picture could be really light. I see more -8s do it than -9s and -10s, and usually with about ~3 hours or less left in a long haul. I’m not sure what TUI’s load factors on that route are. It could be a 787 because it is the only plane that can both fly the route and make it profitable with a small load.