Good catch Ronaldo, My memory failed me on this one and I should have looked at the dates. I do not however see any thing in what I am finding that the carrier cannot file at least an appeal if not an outright petition to determine the existence of single carrier. Frontier did so in 1997. 25 NMB No 3

The only 50% rule I can find is for 1206.2 in determining representation dispute. I believe an argument can be made that this is not a representation dispute as of yet, this is a request for determining if we are still considered a single carrier under Republic Airways. I believe the NMB will hear this, but only time will tell.

§ 1206.2 Percentage of valid authorizations required to determine existence of a representation dispute.
(a) Upon receipt of an application requesting that an organization or individual be certified as the representative of any craft or class of employees, a showing of proved authorizations (checked and verified as to date, signature, and employment status) from at least fifty (50) percent of the craft or class must be made before the National Mediation Board will authorize an election or otherwise determine the representation desires of the employees under the provisions of section 2, Ninth, of the Railway Labor Act.
(b) Any intervening individual or organization must also produce proved authorizations (checked and verified as to date, signature, and employment status) from at least fifty (50) percent of the craft or class of employees involved to warrant placing the name of the intervenor on the ballot.
[77 FR 75549, Dec. 21, 2012]

Any links or text copies to rules you have supporting an opposite position would be very welcome.

What is Document 118?