Vandals spray-painted Arabic slogans, including one that when translated read "Death to Jews," inside the cargo bay of an El-Al passenger plane, The Earth Times reported.
Airline staff noticed the anti-Semitic slogans while loading luggage onto the plane at Milan's Malpansa Airport before traveling back to Tel Aviv.
Authorities believe the incident likely happened shortly after the plane landed in Milan.
El-Al, considered one of the world's most secure airlines, is asking for an immediate investigation into the incident.
The Earth Times' report cited an article about the incident in the Israeli newspaper Yediot Ahronot daily.