Stack overflow error - Turbo Pascal

program pr13;
uses crt;
type Tair = record
     flight: string;
     arr: string;
     t_dep: string;
     t_arr: string
     end;
TairAr = array[1..20] of Tair;
procedure proc(table: TairAr; nt: byte;
          var arr: TairAr; var na: byte; s2:string);
var i, j: byte;
    zap: Tair;
begin
j:= 0;
for i:= 1 to nt do
    if table[i].arr = s2 then begin
       inc(j);
       zap:= table[i];
       with arr[j] do begin
            flight:= zap.flight;
            arr:= zap.arr;
            t_dep:= zap.t_dep;
            t_arr:=zap.t_arr;
       end;
    end;
na:= j;
end;
var
i, nt, na: byte;
table: TairAr;
arr: TairAr;
fl: file of Tair;
s,s2: string;
begin clrscr;
write('enter file name-> ');
readln(s);
assign(fl, s);
rewrite(fl);
i:=1;
while true do begin
     with table[i] do begin
          writeln(i,'-i flight:');
          write('enter flight code -> '); readln(flight);
          if flight = 'z' then break;
          write('enter arrival destination -> ');
          readln(arr);
          write('enter departure time -> ');
          readln(t_dep);
          write('enter arrival time -> ');
          readln(t_arr);
          write(fl, table[i]);
          inc(i);
     end;
end;
nt:= i;
Write('search for town: ');
Readln(s2);
proc(table, nt, arr, na, s2);
writeln(':');
for i:= 1 to na do
    with arr[i] do
         writeln(flight:3, arr: 10, t_dep:5, t_arr:5);
close(fl);
readkey;
end.