They have 14 airports so far, only 3 of which are international, so >10 domestic :)

In all seriousness, they've only been flying for three years. Give 'em time.

Those ten airports serve, just guessing here, 1/3 of the US population.

1/3rd might be high, but easily 1/4th. The only major metro areas they're missing are Denver, Chicago, and Atlanta.

Am I going to have to figure it out? Fine.

JFK: 19M

SFO: 4.3M

LAX: 13M + 4.5M (adding Riverside, San Bernardino, Ontario for charity's sake)

San Diego: 3M

DFW: 6.5M

SEA: 3.4M

BOS: 4.6M

DC: 5.5M

Orlando: 2M

LAS: 2M

FTL: 5.5M (counting Miami)

That's 73.3 million people, so adding in the few we underestimated (eg you can drive to SFO from San Jose if you feel like it) then 1/4 is actually pretty good.