Entities:

Member

MemberID (Primary Key)
FirstName
LastName
Email
ContactNumber
SmokingPreference
MusicalTaste
ChitchatPreference
Helicopter

HelicopterID (Primary Key)
FlyingLicenseNumber
ExpiryDate
Maker
Model
Color
YearBuilt
OwnerID (Foreign Key referencing MemberID)
City

CityID (Primary Key)
Name
State
Country
FlightRequest

RequestID (Primary Key)
MemberID (Foreign Key referencing MemberID)
HelicopterID (Foreign Key referencing HelicopterID)
StartCityID (Foreign Key referencing CityID)
DestinationCityID (Foreign Key referencing CityID)
DateAndTime
AvailableSeats
MaxLuggageWeightPerHead
ContributionPerHead
Status (Pending, Submitted, Accepted, Rejected)
PromoCode

PromoCodeID (Primary Key)
Code
DiscountAmount
MaxDiscountAmount
ValidityStartDate
ValidityEndDate
IsUsed
MemberID (Foreign Key referencing MemberID)
EnRouteCity

EnRouteID (Primary Key)
FlightRequestID (Foreign Key referencing RequestID)
CityID (Foreign Key referencing CityID)
Relationships:

Member-Owns-Helicopter: One-to-Many relationship between Member and Helicopter.
Member-Creates-FlightRequest: One-to-Many relationship between Member and FlightRequest.
Helicopter-PartOf-FlightRequest: One-to-Many relationship between Helicopter and FlightRequest.
FlightRequest-StartsFrom-City: Many-to-One relationship between FlightRequest and City.
FlightRequest-Destination-City: Many-to-One relationship between FlightRequest and City.
FlightRequest-EnRouteCity-City: Many-to-Many relationship between FlightRequest and City through EnRouteCity.
Member-Uses-PromoCode: One-to-Many relationship between Member and PromoCode.