When the soldiers jump from the helicopter, the door is shown to be on hinges rather than a sliding door. The force of the rotor wash plus any lateral motion would force an unsecured hinged door to slam shut almost instantly.
When the women are in the helicopter they are shown casually chatting among themselves without headsets. In a non-insulated utility chopper such as the one shown, they would be unable to hear even the person next to them without shouting.
As has already been established in an autopsy scene and elsewhere, witches have extraordinarily sophisticated hearing. Their ears are structured differently to normal humans. This allows them to hear and distinguish between a very wide range of sounds which would be inaudible to humans. It's therefore reasonable to presume that the noise in a helicopter would not prevent them from hearing each other. Likewise their vocal range is vastly larger than humans, allowing them to talk in frequencies humans wouldn't be able to hear.
The flag being folded is the current, in real life, flag and shows 50 Stars for the States of the Union, within the Series' continuity there are far fewer, but larger, states, as shown on the title sequence.