Reporting that United Airlines has been flying weapons parts to Israel on passenger planes has raised alarm that civilian jets could become targets in the Middle East conflict.

• Documents show several shipments headed to Israeli arms maker Elbit Systems, carried aboard civilian flights.
• If true, groups like Hezbollah, the Houthis, and Iran could treat those planes as legitimate military targets.
• The worry is not a one-off: multiple shipments were scheduled, suggesting a pattern rather than a mistake.
• A downed airliner could be used as a trigger for a much bigger war, including a ground invasion.
• The broader risk is a chain of separate conflicts — Ukraine, the Middle East — pulling in allies the way the First World War began.

Outlook: Pressure will build on United and other carriers to stop the shipments, but the risk to civilian flights stays high while the fighting continues.