Gents, no offense...and I mean that... but nothing in this thread is factually correct.
This is my 10th year with the agency and I have no plans to ever leave. I've known a few that didn't make it past string or quit within a year or two but it was almost always something they did or they couldn't adjust to the bureaucracy that comes with any gov job.
When a job gets posted, the pay grade listed in the offer has VERY LITTLE room, if any, for negotiation. The FAA HR just isn't comparable to a civilian HR dept.
Trust me, if the job is listed at a GS13 step 5, you aren't negotiating to a step 7. You either take it or not.
The FAA has done some things very recently to attract potential inspectors that I thought I'd never see. That goes to show how short staffed we are. Especially for OPS Inspectors.
ETA
In general, as an OPS inspector new hire (with air carrier, 135, 91k, or military) you can almost guarantee starting at GS-13 Step 5 plus the applicable locality pay.
Some openings may be listed at the GS-12 level. If so, you could expect a promotion to GS-13 after your first year.