It is safe to assume that the warning related to the possibility that terrorists belonging to one of the Islamist groups operating in Sinai will fire shoulder-launched missiles at airplanes. Some of these terrorists are directly linked to al-Qaeda , but most belong to Bedouin Salafist groups whose members are Egyptian citizens who live in Sinai.
These groups have received large amounts of weapons from Iran and Libya over the past two years, mainly with the purpose of transferring the arms to Gaza through the Philadelphi Route's underground tunnels. Some of the weapons remained in Sinai, hidden, and are used by Islamist groups, mainly Ansar Bayt al-Maqdes (Supporters of Jerusalem), to carry out terror attacks against the Egyptian authorities and military, as well as against Israel.
Among the weapons smuggled from Libya into Sinai are old Russian-made SA7 "Strela" anti-aircraft missiles. Most likely, the Islamists in Sinai also received more advanced models of the missiles – SA18 and SA16. One of these more advanced missiles was fired two years ago at an Israeli helicopter during the terror attack in the Ein Netafim area – carried out by a Salafist group based in Sinai.
Planes en route to Eilat's airport arrive from the south and are in the range of shoulder-launched missiles, if they are fired from Sinai. The mountainous terrain would make it very difficult to detect anyone trying to fire missiles at Eilat-bound aircraft.
It is very possible that Israeli intelligence agencies obtained information regarding a plan to open fire on Eilat-bound civilian aircraft and therefore ordered the temporary closure of the southernmost city's airport. It is safe to assume that such an attack, if it was in fact in the works, would not be directly linked to the warning that led to the closure of American embassies in the Middle East.
The jihadist and Salafist Bedouins in Sinai are currently engaged in a violent confrontation with Egyptian security forces trying to rein in the terrorists. The Egyptian forces have caused heavy casualties among these groups, which are looking to further deteriorate the relations between Cairo and Jerusalem, this in addition to their continued attempts to kill Israelis and disrupt daily life and the economy in Israel. In this case, they are trying to hurt tourism in Eilat. In light of this, Israel plans to have all Eilat-bound planes land at the airport in Ovda, located dozens of kilometers to the north. Plans for the long term include closing the airport in Eilat and building a new one north of the city, in the Arava. The order to shut down the airport in Eilat was most likely based on credible intelligence.