Originally Posted by
JustAMushroom
We have run out of numbers....kind of. Many simmilar ones 3899,3988..etc. ATC asked HQ to figure out a solution and the solution was the letter added to the last two number "88F" of "99c"
Originally Posted by Ellen
In the SLC area especially (Training tower for FAA), ATC has given instructions to wrong A/C and flights have also responded to clearances NOT for them.
Thanks for the insight. After looking a little more closely, it appears the number-letter combo is used almost exclusivley on Skywest flights out of SLC. Nearly all the flights into SLC are all numeric. I didn't realize SLC was a training tower, it all makes sense now.