The reported shooting down of an Egyptian Air Force helicopter by Islamic militants with a portable surface-to-air missile marks a serious escalation in the challenge facing the Egyptian military.
It is fighting what amounts to an Islamist insurgency fused with wider lawlessness in the Sinai Peninsula.
Egyptian forces have relied heavily on US Apache gunships and various Russian helicopters in their battle with the militants.
But the apparent use of shoulder-fired surface-to-air missiles by insurgents dramatically raises the stakes in this increasingly bloody struggle.
Evidence for the use of a "manpad" - a "man-portable air defence system" - in shooting down the helicopter, which the army admits crashed, includes a video posted online by the militant group Ansar Beit al-Maqdis, apparently showing the incident.
The group claims to have downed the helicopter in northern Sinai, near the border with the Gaza Strip.
The military remains tight-lipped but well-placed sources in Cairo are quoted in the New York Times acknowledging that the helicopter was brought down by a Russian Strela-2 missile, also known as an SA-7 by Nato.
A potent weapon
This is not the first time such weapons have been used in this part of the world. In October 2012 the Israeli military claimed an SA-7 had been fired at one of their aircraft operating over the Gaza Strip, blaming Hamas.
The SA-7 and the many similar weapons based on it, is an ideal weapon for insurgents - light, portable and easy for one man to fire.
It homes in on the heat generated by an aircraft's engines and can reach altitudes of above 2,000 metres.
Such weapons are a staple of Soviet-equipped armies, including the Egyptian military itself, and they remain a potent weapon despite their age.
It is feared that the 2011 civil war in Libya resulted in the release of large numbers of these types of weapon, when arms depots were overrun by rebel forces.
The US and other Western governments tried to contain the proliferation of "manpads" after that conflict, but it is likely they only had limited success.
They have been tracked flowing south to the conflict in Mali, and Israeli intelligence experts believe many may have ended up in the Sinai Peninsula and the Gaza Strip.
Perhaps the biggest fear around the spread of such ultra-portable missiles is the threat they pose to airliners, particularly when landing or taking off. In 2003, a Strela was fired at an Israeli passenger aircraft in Kenya, but missed.
Tourism could be impacted, since many tourists fly to south Sinai resorts on the Red Sea coast.
Dutch charter airline Transavia cancelled its flights to the south Sinai resort of Sharm el-Sheikh in October because of the threat of such attacks.
For now though it represents a big jump in the hurdle faced by the Egyptian military.
Having to curtail its use of helicopters would significantly impair the Egyptian military's ability to hit insurgent targets, at a time when they are already taking significant casualties in the Sinai.
It might be encouraged to use faster jets instead, which might increase the risk of collateral damage.
At the very least, it may have to alter its tactics and upgrade the defensive equipment on the ageing Russian helicopters in its fleet.
The attack came at a particularly violent for Egypt. On Saturday, as people in Cairo celebrated the third anniversary of the protests that toppled former President Hosni Mubarak, 49 people were killed in clashes over the deposing of his successor, Mohammed Morsi.
In Sinai itself on Sunday, a bus carrying soldiers was attacked, killing four of them.
And on Friday, a series of bomb attacks in the capital left six dead, a police headquarters destroyed and an Islamic museum badly damaged.