Narrative: ON BOTH DAYS WE WERE SLOWED DOWN TO MINIMUM FORWARD AIRSPD TO FOLLOW BEHIND ONE DC9 OR ONE MD88. THIS SLOWDOWN COST US 24 MINS AND 4000 LBS OF FUEL AND 15 MINS AND 3000 LBS OF FUEL RESPECTIVELY. HOWEVER AT THE DISTANCES INVOLVED WE COULD HAVE EASILY OVERTAKEN THE ACFT ... .