IF you must mob,
USERRA does protect you from discrimination on hiring based on military service. IF they toss you from the pool based solely on your military service mob, you may have a discrimination complaint.
Example: "Hey, I have military service and cannot be available in the pool status until XYZ", IF they send a letter dropping you from the pool, and the date corresponds to your informing them, you have some evidence of discrimination for DOL VETS.
You have the burden of proof, so would need to try to find if they drop other pool applicants for non military reasons. You could attempt to compel this from the airline in your complaint.
Here is your reference under USERRA
"No employer may deny a person initial employment, reemployment, retention in employment, promotion, or any benefit of employment based on the person’s membership, application for membership, performance of service, application to perform service, or obligation for service in the uniformed services.
38 U.S.C. 4311(a)
Good luck, you do have some USERRA protection, but you also have the burden (challenging) but not impossible.
Good luck
SD