You should contact Approach or Tower in good time—normally at least 5 minutes before you expect to enter the control zone or need to descend into controlled airspace. This gives ATC time to plan your entry, sequence you with other traffic, and issue approach clearance or joining instructions.
If you call too late (less than 3 minutes away), ATC may not have time to brief you properly. If you call too early (15 minutes out), you may confuse the picture. Five to 10 minutes before your estimated time to overhead or the control zone boundary is ideal.
What to Say in Your Initial Call
Your initial call must establish communication and provide essential information so ATC can service you. The format is: