EXTRAORDINARY late Mandate / 1948 War 'Destinaire Parti' incoming Arab airmail: 1 IV 1948 registered [airmail] cover on "Imperial" stationary from BAINO (BEINO) Lebanon to HAIFA, addressed in Arabic to "His Excellency Iskandar Kurdush" (return addressed to the sending locale in Akkar, Lebanon), franked 55p using horizontal pair 25p + 'orphan' 5p - appears to be 50p for the period registered airmail rate (as seen on other period "airmail" marked covers; incoming surface mail to Palestine ceased on April 15th & airmail on the 25th; sea mail/surface mail from Lebanon ceased on April 7th) + 5p for then new 'Palestine Relief' surcharge (this based on an earlier 1945-47 obligatory surcharge for the Lebanese Army, now applied on all domestic and foreign letters & post cards: the initiative primarily used the original Army Stamps with a new overprint, starting May 1948 but civilian franks were also used - here very early usage for this initiative), tied by 3x strikes of the local postmark on the front + the registry label; the back is tied by an unclear postmark possibly dated 14 April ("14 IV") and may be from the provincial capital of HALBA (Baino is a tiny locale in this northern-most district, which is the poorest and most rural of Lebanon's provinces).
The cover was subsequently backstamped 28 APR 48 REGISTERED HAIFA arrival, proving that the cover did reach Palestine: this quite extraordinary as registered airmail service ended on 24 April & LYDDA airport closed on the 25th (officially ending Mandate era airmail). One clue as to this cover's transit is offered by Zvi Aloni in his book on Air Mail in Eretz Israel (p.100): the same day Lydda airfield closed, Air France transferred its services to TEL AVIV (Sde Dov) & HAIFA airports (until Lydda reopened in November). As such, this may be the way by which this cover reached Palestine. Siegel & Shamir (IFPL p.9/12) noted that BOAC civilian services at LYDDA actually ended on 28 April (this was the last company to do so), and their staff was evacuated around 4:30pm (and some military flights continued to land there on into May) - however, Lebanon being Francophile, the Air France postal link via HAIFA seems more plausible in the case of this cover.
Nevertheless, at this time during the War of Independence & the flight of Arab residents from Haifa, much mail to Arabs or Arab locales in the area could not be delivered/was not claimed & was marked by the Haifan Mandatory instructional marking "RETURNED TO SENDER | NO SERVICE" (the 'Destinaire Parti' / Addressee Absent marking was not used at the Haifa head post office) type F-I in black (the similar type F-III in violet was used in Tel Aviv): here such stamped 2x on front + 1x on back.
Per manuscript pencil notations on the back it appears there were at least 2 attempted deliveries, in additional to the initial notice (sent by the Mandate post service, which functioned in Haifa until May 5th): on "13/5" (eg. by the interim/Minhelet Haam postal service) and "2/6" (by the Israeli postal service) before the cover was marked by the Mandate-era French form handstamp "Non Reclame" & marked "90 Unclaimed" in blue crayon on the front + RLO (Returned Letter Office) in red crayon. Unlike similar mail from Haifa this cover was not censored by Israel.
Rare postal history documenting the Arab flight from Haifa, incoming airmail via a generally unknown period route & postal markings/handling from 3 postal periods; less than 30 covers with the F-1 IM are known (see Kibble p.6 for a similar cover). Backflap torn, but cover complete & very fine.