Originally Posted by
flyerCO
No that's not discretion. Discretion would mean they could allow you to fly despite not having the correct documents.
Legally when flying only a passport is acceptable, even for Canada. Nexus cards, passport cards, drivers licenses, etc are good only for land and sea crossings.
That is not true. Nexus cards are good for entry via air travel too.
When flying into Canada, Canada accepts US birth certificates with just a regular US driving license. It's been the air carriers that frustrated such travel by air into Canada without a passport and/or Nexus; and it's been the USG that has frustrated such travel by air into Canada without a passport or NEXUS.
Originally Posted by
flyerCO
They don't have to worry about US citizens because there's the possibility going to return via land crossing, or that will even apply for work permit at border crossing.
That's not always true either. And they sometimes ask this even of US citizens.