# Block 4

US F‑35 Deliveries Hit by Missing Radars as Block 4 Upgrades Stumble

Deliveries of F‑35As to the U.S. Air Force have included airframes without the planned APG‑85 AESA radar because of development delays and cost overruns in the Block 4 upgrade. The absence of onboard radars forces operational compromises, underscores long‑standing concurrency problems in the programme, and complicates future upgrades and budgeting.