This pension funding argument is being used by some to muddy the waters of ANSP charges.
Government owned ANSPs are not generally run as businesses. Privately owned ANSPs are run as businesses.
A business should generate enough profits to cover their costs such as pensions.
It seems to me some businesses want retain all their profit for their shareholders and for their customers to stump up for their pension costs with pass through.
I can fully understand the airlines position. They want lower charges. They always will. They see ANSPs making huge profits and they wonder why those profits are not going to pay the pension liabilities.