The European Union has warned governments against lavishing emergency aid on airlines to make up for losses from disruptions in operations caused by the eruption of a volcano in Iceland. But it proposed other measures to help them recover from the weeklong shutdown of air travel. The European Commission’s own estimate of losses ranged from €1.5 billion to €2.5 billion, taking into account losses by airlines, airports and tour operators, said Siim Kallas, the EU transport commissioner. Air traffic levels in Europe have been back to normal since Thursday, according to Eurocontrol, the agency responsible for coordinating European air traffic management. According to the agency, more than 100,000 flights were canceled from 15 April 15 to 22 April. Seeking ways to help airlines without giving one carrier an advantage over others were key said Kallas, adding that airlines should be allowed to expand their use of night flights to ensure that stranded passengers were returned home and backlogs of freight could be delivered. He also proposed temporarily easing the rules governing the way takeoff and landing slots were allocated at airports. Other measures to help airlines with short-term cash-flow problems could include temporarily deferring the so-called en-route charges normally paid by airlines to air traffic control, he said.