Claimed battery is 21 mins, but real world it's more like 15-16.
Default range depends on what country you're in and whether the drone is on FCC or CE mode....plenty of threads on that subject on the forum and currently it's easy to change from one to the other...for now anyway.
You question does not have a clear answer
Your flight time will depend on how high above sea level, how hot it is - thins our the air.
Battery chemistry is effected both by heat and cold, both lower it abilitys.
And it depends on how low you are willing to run the battery before you land. Some people 30%, some 20% and other 10%.
The distance is effected by the radio mode (Europeans I think have a lower output than Americas by law) and also where you are flying. In a heavy Radio Freq area like a city, that will degrade more than the wide open fields in the middle of no where.
So, I think you will find that your results WILL vary.
But I can assure you that the Mavic air is a fine craft that will average out 16 to 17 min and fly well within the legal distances of many countries without much if any drama. Assuming you know how to position your antenna (not cross them on the transmitter and point them towards your craft) and fly at a reasonable height so that the radio waves are not absorbed into trees and buildings.
If you are TRULY worried about flight time and distance - get a Mavic Pro. That technology is way better for battery and RF than the Mavic Air. I fly Inspire 2, Mavic Pro and Mavic air - and Mavic Pro is much better than Mavic air for battery and distance.
Enjoy, what ever you decide. I'm really happy with my Mavic Air and fly it way more than the Mavic Pro despite the apparent advantages of the Mavic Pro - Mavic air is a better camera and gimbal for example, and higher bit rate looks nicer in videos... (Mavic II may change this, another month before we know if they are making one this year for us!).