What is m.insert number?

When I’m flying, often I have my speed on like around 250-260 knots for short haul, and around 300 for long haul. But, whenever I go to let’s say put my speed up, it says m.number. please help I don’t know what it is.

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That’s your Mach Number. It activates right after FL280.

And what is fl280?

28000 feet MSL

Here’s a little wiki article about that if you’re into it… Not sure why anyone would be into Wikipedia tho…

Flight Level 280. 28,000 feet above sea level.

Ok thanks. So what speed is what number or how do I check?

Your airspeed will still show as expected to the left on your HUD. Your Mach Number and Ground Speed (GS) will show below the left column

You typically want to cruise at M.79 if you are in any A319-21 or 737

…And .84 in most heavies

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Ok thanks for your help. this can now be closed

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You learn something new everyday!

That’s for sure!

Awesome. Be sure to check out the #tutorials section and feel free to DM if any more questions should be asked. LOADS of info for you to check out there. Welcome to the glorious Infinite Flight Community!

The speed of sound is not constant, but depends on altitude (or actually the temperature at that altitude). At sea level, it’s about 760mph, whereas at 30,000ft it’s closer to 680 🤷
So you’ll hit Mach 1 at a lower speed at higher altitude. Not sure if that’s of much use, just thought it was interesting.

Just adding a link to another thread that has recommended Mach cruise speeds for all aircraft in Infinite Flight that you might want to have a look at! Cruise Speeds

Ok thanks this can now be closed

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OP requested closure.