Circumnavigate the earth

[mcraig]

Anyone know how long it would take the fastest airplane in existance to travel around the earth?

[buildersmate]

5.51 hours

Assumptions
1) The fastest conventional aircraft was the X-15 at 4520 miles per hour.
It didn't need to be refuelled (it would have needed this)
The circumference of the earth at the equator is 24901 miles
The plane travelled at or near sea-level.

[dundurn]

The X-15 didn't leave the ground under its own power - it was airlifted by a B-52. There is the small problem of range as well - it didn't go very far! If you're allowing the X-15 as a candidate, what about the space shuttle? It does circumnavigate the globe and on its final orbit when it glides home it goes around the world in under 2hrs.

For planes that can do the journey 'under their own steam' Concorde holds the record at just under 32 hours. It couldn't air to air refuel so had to land every so often to top up.

A Lockheed SR-71 Blackbird with air to air refuelling could (theoretically) do the trip in about half the time, say 17 hours, but you'd probably have to put it in for a major refit at the end.

[buildersmate]

I just answer the question, stating what assumptions I have made. Of course it is possible to devise many answers to this.