Originally Posted by
Yaatri
Wirelessly posted (Samsung Galaxy S: Mozilla/5.0 (Linux; U; Android 2.3.6; en-us; SGH-T959V Build/GINGERBREAD) AppleWebKit/533.1 (KHTML, like Gecko) Version/4.0 Mobile Safari/533.1)
That's a bad statement to make. This classification is not universal.
Y and F were are as close to universal as you're going to get, and virtually all non-low-cost airlines use these for the basic, interline-able, full-fare coach and first respective.
There is actually a standard for these things (google on "IATA Resolution 728 Code Designators for passenger ticket and baggage check") but airlines alter how they use them pretty much at will. (Trivial example -- with no supersonic service any longer, R is now Premium Economy on some airlines and 1st-class-suites on others.)
LCCs that don't sell through the GDS systems may or may not use this kind of fare code at all.