Which information is in the flightplan send from Skydemon? When I am flying on a filed flightplan they always ask for no of persons onboard. That number is stated in the flightplan page but apparantly not send??

Number of people on board is part of the flightplan supplemental information. This should not technically be sent in the initial filing, but we send it to certain countries who have told us they want it. Regardless, any recipient can query our system for this information using standard ICAO messages. If there is a country who you believe wants that information right away, let us know, and our flightplan people will be in touch with them.