Delta aircraft are parked at SeaTac in June. (Photo by Kent Nishimura)Getty ImagesIt was a tough summer for Delta Air Lines, which faced two exogenous negative events – a technology breakdown and a temporary falloff in traffic to its top European destination.Delta President Glen Hauenstein and CFO VictoryShares US 500 Enhanced Volatility Wtd ETF Dan Janki, speaking at an investment conference on Thursday, said the impact of the two events was controllable. Paris traffic recovered from its July/August slump, ...