Air India flights mumbai london mumbai - Entertainment systems not working on long flights

We were travelling from mumbai to london to attend the convocation of my elder daughter at the prestigious imperial college of London on the **th April **** vide Air India flight no *** . It was a long direct flight of almost * hours. After taking off for a long time we tried switching on the entertainment system but to no avail. We complained several times about this to the crew . Their common reply was WE ARE REBOOTING THE SYSTEMS. After an hour the pilot announced some problems with the entertainment system so no TVs for majority travellers on a * hour flight. After a week on our return flight from London to mumbai on Air India flight no *** on *th may **** to our greatest surprise the it was déjà vu. Almost **% tv sets were not working. The staff themselves advised us to register complaints with the airlines. Totally disgusting from a company that is owned by the Tatas. Am going to forward this complaint to the chairman of the company.