sql - PostgreSQL constraint problems -

i having these 2 errors :

error: there no unique constraint matching given keys referenced table "flight"

*** error ***

error: there no unique constraint matching given keys referenced table "flight"

this code :

create table staff (  employeenumber int not null,  firstname char(15) not null,  lastname char(15) not null,  socialsecurity int not null,  sex  char(1) not null,  address  char(20) not null,  city  char(20) not null,  province char(15) not null,  country  char(20) not null,  primary key (employeenumber)  );  create table flightattendent (  faln  int,  staffrole char (20) not null,  employeenumber int not null,  foreign key (employeenumber) references staff(employeenumber),  primary key (faln)  );  create table aircrafttype (  actype  char (10),  instrument char(1) not null,  engines  int not null,  crewcount int not null,  passengercount int not null,  primary key (actype)  );   create table pilot (  piln  int,  medicalvalid date not null,  staffrole char (20) not null,  employeenumber  int not null,  aircrafttype char (10) not null,  foreign key (employeenumber) references staff(employeenumber),  foreign key (aircrafttype) references aircrafttype(actype),  primary key (piln)  );  create table aircraft (  aircraftid  char(6) not null,  aircraftmanufacturer char(10) not null,  aircrafttype  char(10) not null,  foreign key (aircrafttype) references aircrafttype(actype),  primary key (aircraftid)  );  create table airport (  airportcode char(4) not null,  airportname char(40) not null,  city  char(20) not null,  country  char(20) not null,  continent char(20) not null,  primary key (airportcode)  );  create table flight (  flightid  char (20),  flightdate  date,  aircraftid  char(6) not null,  arrivalairport  char(4) not null,  departureairport char(4) not null,  primary key (flightid, flightdate),  foreign key (arrivalairport) references airport(airportcode),  foreign key (departureairport) references airport(airportcode),  foreign key (aircraftid) references aircraft(aircraftid)  );   create table flightcrew (  flightid char (20) references flight(flightid) on delete cascade,  flightdate date references flight(flightdate) on delete cascade,  employeenumber int not null,  staffrole char(20) not null,  primary key(flightid, flightdate),  foreign key (employeenumber) references staff(employeenumber)  );  create table passenger (  passengernumber int,  passportnumber int not null,  citizenship char (20) not null,  firstname char (20) not null,  lastname char (20) not null,  primary key (passengernumber)  );  create table passengermanifest (  flightid char(20),  flightdate date,  passengernumber int not null,  foreign key (flightdate) references flight(flightdate),  foreign key (passengernumber) references passenger(passengernumber),  primary key (flightid, flightdate)  ); 

what did wrong? thanks!

when have multiple values in primary key, need reference differently foreign key.

basically, when say

flightid char (20) references flight(flightid) on delete cascade, 

postgresql checks primary key, doesn't exist (since primary key on table (flightid, flightdate)).

so drop references clauses when referencing flight table, , add

foreign key (flightid, flightdate) references flight (flightid, flightdate) 

in manner have in of other table definitions.