Many airlines require US Citizenship. The above will lead to a Green Card, assuming you have applied. Then need 3 years married and 18 months physically in the US as Green Card holder before you can apply for Citizenship - application processing can take up to one year.
Respectfully, that's incorrect on both accounts. No airline that I'm aware of can actually require you to be a US citizen as a pre-requisite to employment. It's illegal. I'm pretty sure they can require you to be a citizen to do the CRAF stuff, though
Also, I was married for 2 years before I got my permanent GC and could apply for citizenship after 5 years of being a permanent resident. This may have changed, though.