Southwest Airlines (LUV) fell about 5.5% in the latest session as airline stocks weakened on higher expected fuel expense after jet-fuel and crude prices jumped amid escalating conflict involving Iran. Because fuel is one of the largest variable costs for carriers, rapid fuel-price moves can immediately compress margin expectations and trigger sector-wide de-risking even without company-specific news.

Separately, investors are again focused on aircraft supply risk after Boeing paused 737 MAX deliveries to inspect and rework undelivered jets due to small scratches on wiring bundles from a machining error. Boeing said in-service MAX aircraft can keep flying, but the delivery interruption is expected to reduce near-term deliveries, reinforcing the risk that carriers dependent on Boeing narrowbodies may face timing mismatches in capacity growth and fleet renewal.

Southwest operates an all-Boeing 737 fleet and has flagged in its filings that prolonged delivery delays or MAX availability issues could materially affect its business plans. With the company’s strategy leaning on product and network changes while it modernizes the fleet, any delivery slippage can increase the time Southwest must run older aircraft, potentially raising maintenance costs and limiting unit-cost improvement just as fuel costs rise.