[DB]

Commercial airliners would be the easiest.

Planes take off from all over the world and land here.

It can't be that hard to replace the passengers with a nuke at the start and fly into US airspace as a standard scheduled flight. No suspicion as it is allowed to fly over/into any major city in the country.

Game over.

An oil tanker would make a good transporter as well (other than being sea level at detonation). There's no way to tell what's buried in millions of gallons of crude oil. Inspection would be impossible. There's plenty of major oil ports near large cities.

The bottom line is trying to prevent a nuke from getting into the country by inspections or interceding at the border is basically impossible. It is a waste of resources pursuing an impossible goal.

The only hope is taking them out at the source long before they get here.

[RHINO369]

They'd be better off buying a small private jet and just detonate on approach to Reagan national. We wouldn't even know what the hell happened.

[sig226]

"The only hope is taking them out at the source long before they get here."

Agree 100%.