Can you enter the Delta?

What it takes to enter Class D

14 CFR 91.129(c)(1) asks for one thing before you enter Class D: two-way radio communication with the tower, maintained while you're inside. There's no entry clearance. That's the difference from Class B, where you need to hear "cleared into the Class Bravo" before you go in.

When communication is established

AIM 3-2-5 answers this with the exact call from the quiz. If the controller replies "[your call sign], standby," communication is established and you can enter.

Two replies keep you out:

• "Aircraft calling Caldwell Tower, stand by." Tower didn't use your call sign, so communication isn't established.
• "[Your call sign], remain outside the Class Delta airspace and standby." Communication is established, but you've been told to stay out.

The call sign is what matters. "Stand by" on its own doesn't keep you out.

What to do after "stand by"

Keep coming inbound and plan your entry for the runway you got from the ATIS. Tower knows you're there and is fitting you into the sequence. Don't start orbiting inside the Delta without telling them, since that puts you somewhere tower doesn't expect you. If you're unsure, ask.

Make your first call early. The AIM says to call far enough from the boundary that you won't enter before communication is established. An example call, "Caldwell Tower, Skyhawk 172RB, 10 north with information Bravo."

You still need a landing clearance

Entering the Delta and landing are separate permissions. Under 91.129(i), you need a clearance from the tower before you land, so "stand by" lets you in but doesn't clear you to land.