Just a WAG on numbers but here's an estimate on why:

DAL cost for a 777 roughly $210 million. (list 230-270 million)

Looking at 10Q: terms are quarterly payments on a 12 year note.

Commercial loans even in good economies are 7-10%.

So: 210mil at 8.5% over 12 years paying quarterly =

Payments of $5,951,716 quarterly

Interest over the life of the note: $107,682,391

x2 airplanes = $215,364,782 INTEREST EXPENSE!

Or in other terms: The cost of yet another 777-200LR.

Dave Ramsey would be proud of Delta for this.