MySQL stored procedure skips id's when auto incrementing

Question

I'm having some problems with my stored procedure. Hope anyone can help me figure out what the problem is.

I use the data from weekly_schedule as a template for how fill my flight-table. I do this by calling CreateFlights(). All data get inserted as expected, so I'm not missing any data, but for some reason every third row is skipped despite the fact that I use auto_increment on flight.id.
(flight.id = 1,2,4,5,7,8,10,11 ... 472,473,475,476...
flight.id = 3,6,9,12 etc. are not null, they're simply just not there.)

I can't figure out why I get the holes in the id-sequence. Can anyone help me understanding what happens? I want the flight-id's in a continuous sequence.

Here is my code..

---

CREATE PROCEDURE CreateFlights()
BEGIN
  DECLARE startdate date DEFAULT curdate();
  DECLARE enddate date DEFAULT date_add(startdate, interval 367 day);

 WHILE startdate <= enddate DO
 INSERT INTO flight(`id_weekly_flights`, `flightdate`)
  (select `id`, startdate  
   from `weekly_flights`
   WHERE `name_weekdays` = dayname(startdate)
   AND `fl_year` = year(startdate));
 SET startdate = date_add(startdate, interval 1 day);
 END WHILE;
END //

---

CREATE TABLE weekly_flights (  
id int NOT NULL AUTO_INCREMENT,  
departuretime time,  
fl_year int,  
name_weekdays varchar(9),  
id_route varchar(8),  
PRIMARY KEY (id),  
FOREIGN KEY (name_weekdays) REFERENCES weekdays(name),  
FOREIGN KEY (id_route) REFERENCES route(id)  
)  
ENGINE=INNODB;

CREATE TABLE flight (  
id int NOT NULL AUTO_INCREMENT,  
flightdate date DEFAULT NULL,   
id_weekly_flights int,  
PRIMARY KEY (id),  
FOREIGN KEY (id_weekly_flights) REFERENCES weekly_flights(id)  
)  
ENGINE=INNODB;

---

INSERT INTO weekly_flights(departuretime, fl_year, name_weekdays, id_route)  
VALUES  
(073000,2010,'Monday', 'LIN2STH'),  
(073000,2010,'Monday', 'STH2LIN'),  
(073000,2010,'Friday', 'LIN2STH'),  
(073000,2010,'Friday', 'STH2LIN'),  
(210000,2010,'Sunday', 'LIN2STH'),  
(210000,2010,'Sunday', 'STH2LIN'),  
(073100,2011,'Monday', 'LIN2STH'),  
(073100,2011,'Monday', 'STH2LIN'),  
(073100,2011,'Friday', 'LIN2STH'),  
(073100,2011,'Friday', 'STH2LIN'),  
(093100,2011,'Sunday', 'LIN2STH'),  
(093100,2011,'Sunday', 'STH2LIN');

Answer 1

I call a 'non-problem' on this.

Are you aware of the fact, that you are not guaranteed to have consecutive auto_increment values at all? Actually, you are not guaranteed that the next auto_incremented value will be greater, than the one before it. It just works this way sometimes by coincidence.

auto_increment is there to help you generate identity values, that's all there is to it, really.