Hola Antonio,
Spanair does in fact fly from Madrid to Ibiza.
There is only ONE flight per day, and ONLY during the summer months. It leaves in the early afternoon. We found this out the hard way. Iberia never secured our e-tickets and sold them. Never buy e-tickets. If you do, get them to mail the paper tickets to your address and allot ample time for this.
-solopod