Early foreign postal links with Israel: 27 IV 1948 registered airmail cover from VIENNA Austria to HAIFA, franked 4s (an additional frank may be missing) & tied by 2x strikes of the local postmark + censored by the Austrian authorities (marks on front); oddly, posted and accepted 2 days after the closure of LYDDA airport (and the suspension of incoming airmail) & 3 days after suspension of registered airmail service to Palestine, nevertheless received and transmitted onward: backstamped 18-5-1948 HAIFA Head Post Office arrival - most likely carried by the 2nd official CSA Czechoslovakian Airways flight to independent Israel, which landed on Monday 17 May which may also make this a '1st flight' cover from Austria (none known to the cataloguer from the 1st CSA flight of 16 May).
Although sea mail arrived in HAIFA on 17 May with the American ship SS Marine Carp via Beirut & European cities, the CSA air link to Palestine/Israel was ongoing since 5 May with fairly frequent flights, and as Kibble's comprehensive list of mail suspension dates and "no service" markings don't have any information on Austria it's probable that there was no mail suspension and that at worst, at this time mail to Israel was simply held up and transmitted after a short delay. Prague-originating airmail posted 27 April is known to have reached Palestine on 5 May, so here similarly postmarked mail (also via CSA) from Austria was probably held back until an airmail transit could be effected. Interesting & rare postal history.