A TUI Airlines Belgium Embraer ERJ-190, registration OO-JEM performing charter flight TB-6793 from Liege (Belgium) to Alicante,SP (Spain), was climbing out of Liege's runway 23L when the crew stopped the climb at FL120 reporting a cracked windshield and decided to divert to Brussels (Belgium), where the aircraft landed safely on runway 01 about 25 minutes after departure from Liege. The crew advised everything was fine and requested to taxi to the hangar. The airline reported the outer pane of the windshield cracked. A replacement Boeing 737-800 registration OO-JAX departed about 4 hours after landing of the Embraer and reached Alicante with a delay of 4.5 hours. The occurrence aircraft returned to service about 38 hours after landing.