On May 23, 1998, about 0330 eastern daylight time, a Learjet 24-B, N100DL, overran the end of runway 07 on landing roll at Orlando Executive Airport (ORL) in Orlando, Florida. The airplane was owned by AJM Airplane Company and operated by Panther Aviation for the purpose of transporting a human organ transplant team. The flight was conducted under Title 14 CFR Part 135, and instrument flight rules. Visual meteorological conditions prevailed and an IFR flight plan was filed. The Airline Transport Pilot (ATP), first officer and four passengers were not injured and the airplane received substantial damage. The on-demand non-scheduled passenger flight originated in Miami, Florida at 0230. According to the pilot, while on approach to ORL, at 1500 feet MSL, he asked for "full flaps" and noticed that the flap indicator had not moved from the 20 degree position. According to the pilot, the airplane touched down on the first 1000 feet of runway at approximately 115 knots, spoilers were extended and the engines were reversed. The pilot stated, "At 80 knots I put pressure on the brake pedals and they went to the floor with no results." At the pilots' request, the first officer deployed the drag chute followed by application of the emergency brakes. The first officer stated, "Upon downward movement of the emergency brake handle, he felt the airplane yaw. He then pulled up on the handle, evacuating the pressure and negating any braking action." This action took place several times during the landing roll. Gates' Learjet Flight Training Manual (Page 105) states, "In using the emergency brake lever, slow steady downward pressure is required. Each time the lever is allowed to return upward to the normal position, nitrogen is evacuated overboard. Brace your hand so you will not allow the lever to move up and down inadvertently on a bumpy runway." After colliding with the Instrument Landing System (ILS) back course antennae for runway 25, the airplane was evacuated. According to the FAA inspector who visited the site, the right wing main attachment brackets were broken on impact and the wing was pushed rearward approximately 3 inches in the fuselage. Damage to several fuel and hydraulic lines in the wing area was noted. Inspector's noted evidence of hydraulic leak(s) in the aft fuselage, outside bottom of the fuselage and on the drag chute. Sources of leak(s) were not ascertained due to the damage incurred by airplane impact. A possible leak from the front lower brake puck on the right inboard brake was evident. Inspector's activated the emergency braking system several times with no discrepancies and no previous abnormalities in the system noted. No identifiable skid marks from the airplane could be found on the runway or the over run area.