Two months after the Israel Air Force grounded its most advanced fighter jet after discovering carcinogenic material in one of them, officials said Tuesday that the IDF was no closer to ascertaining the cause of the trouble. In March, then-IAF chief Maj.-Gen. Elazar Shkedy decided to ground all F-16I training flights after formaldehyde was found in the cockpit of one of the aircraft. A number of pilots had complained of a bad smell, which the IDF Medical Branch then determined was being caused by a type of formaldehyde known to be carcinogenic in high concentration. Last month, Shkedy approved the F-16I for flights, but continued to ground seven aircraft that were found to have high concentrations of the substance. Two weeks ago, another three planes were grounded, bringing the total to 10 - close to half a squadron. "It is understandable that the pilots are concerned," a senior officer said Tuesday. "We are doing what we can to get the planes operational as soon as possible." The F-16I - called "Sufa" (Storm) in Israel - is one of the most advanced and sophisticated combat fighter jets in the world, alongside Israel's F-15I. Lockheed Martin, the plane's manufacturer, has been involved in the tests of the aircraft alongside the IAF.