Apparently, upperclassmen at the Air Force Academy count as military personnel and are under travel restrictions due to the shutdown. From CNN.
It’s uncertain whether the upperclassmen at West Point and Annapolis fall into that category as well. If so, the shutdown could wreak havoc on their schedules also.
Making them forfeits is pushing it, although the NCAA would probably give Notre Dame an exemption if it came down to it.
Besides, the games can be moved: ND-Air Force can be played on Friday 11/15 (that Saturday is a problem because Air Force plays UNLV the following Thursday), and ND-Navy can be played on Saturday 12/6.
Also, is a Notre Dame win over Air Force a given? Remember, the bowl eligibility requirement is “at least as many FBS wins (plus one FCS team that gives out at least 90% of its scholarships, if applicable, although ND plays only FBS teams this season) as total losses”; the six-win requirement no longer applies.