Flight modes...

When flying the following modes, ATC...

VFR...

• Can ask for frequency change in some circumstanes (if you have requested for transit for example)
• Answers to any request
• Gives local QNH

VFR special...

• Doesn't correct your heading until you leave the expected track
• Asks to descend or climb if you are too far above or below the expected altitude (the altitude of the next waypoint in the flight plan). The ATC will not talk if you are climbing/descending, considering you try to reach the expected altitude.
• Asks for frequency change in many circumstances
• Ask for reporting if the next waypoint is REPORT type or randomly if you fly inside a SID or a STAR.
• Ask for a squawk code

IFR...

All VFR Special events and...

• Asks to follow heading if your heading is too far from the expected one
• Asks you to climb (or expedite your climb!) if you are below the expected altitude. The ATC will not talk if you are climbing/descending, considering you try to reach the expected altitude.
• Ask for frequency change on all circumstances (if frequency is available in the flight plan of course...)
• Asks for holding pattern if waypoint is HOLD type
• Asks for arc DME correction if the track is a DME arc