If you are rolling out of the Pilot Retirement Savings Plan, to IRAs, you can take any after-tax balance and split the rollover to a Traditional IRA for the earnings and a Roth IRA for the principal. There is no tax consequence. If trying to leave it within the PRSP, you cannot split the earnings and principal.
Vanguard will have you set up a separate Roth IRA and a separate Traditional IRA outside the PRSP, and this is where the split will go.

This has been verified thru our R&I committee.