[Prophet in the wilderness]

How many 747s would the DoD need ? 20 ?
How much would this program cost ?
A new 747 - 400 cost around $ 275 million a piece.
The US government ( DoD ) can get a good used 747 from a airline from around ( a estimated or guess estimated cost of )$ 100 million ? maybe less ? .
Lets say they need 20-747s, at about $ 100 million a piece, that's $ 2 billion.
Lets say the whole program initially would cost $ 4 or 5 billion, funded over 5 or 10 years, 5 years, $ 1 billion a year, 10 years, $ 500 million a year to fund the program.
Thats inexspendsive for a program that would protect our country from missiles threats.

[Physicist]

Thats inexspendsive for a program that would protect our country from missiles threats.

It's more of a theater weapon. A scud-buster. I imagine it would make an effective anti-aircraft weapon, too.