An investigation into last year’s Helios air crash will reveal that there were serious lapses in flight safety which led to the Cypriot Boeing 737-300 crashing near Athens last August, sources told Sunday’s Kathimerini. A preliminary 200-page report has been compiled by chief Greek crash investigator Akrivos Tsolakis and his team. The report will be made public in April, but sources told Sunday’s Kathimerini that it concludes that the accident was caused by a pressure valve being left in manual mode and the cabin losing oxygen after takeoff. Although this error should have been picked up in a pre-flight check by the two pilots, sources indicate that the report also apportions blame to Helios and Cypriot authorities for letting airline safety standards slip. All 121 people on board the flight from Larnaca were killed on August 14.