Egypt notified airlines yesterday that GPS jamming is a concern to arrivals and overflights, and warned against conducting RNP/RNAV arrivals or approaches.
The jamming was announced on 24MAY, and is centred on Cairo Airport; the source is unknown.
Similar GPS jamming was conducted, at state level in that case, by North Korea last month, from five locations along the border with the South. South Korea, along with other Civil Aviation Authorities, are looking at an eLORAN based alternative as a backup.
Operators planning flights through the Cairo FIR should monitor NOTAMs for latest.