767/w vs 767/q

Can someone please explain the difference between these designations for the Boeing 767. I quite often see the 767/w slated for a flight, but from time to time I see a 767/q. Thanks in advance

It’s the equipment suffix. Each airplane files one or more with their flight plan. Mostly it lets controllers know what type of navigational equipment has, but there is other information controllers can get depending on what the letter is.

/Q is an aircraft that qualifies for /R and /W. /W is for RVSM and /R is RNP.

Some info on RVSM and RNP:
en.wikipedia.org/wiki/Reduced_Ve … ion_Minima
en.wikipedia.org/wiki/Required_n … erformance

Thanks for your help, much appreciated!