This could be another puzzle piece put in Place By Obama and support of Russia to stop any Israeli warplanes from passing over Syrian air space imo.............

US President Barack Obama has ordered the US Navy and Air Force to accelerate preparations for a limited air offensive against the Assad regime and the imposition of no-fly zones over Syria, debkafile reports. Their mission will be to knock out Assad’s central regime and military command centers so as to shake regime stability and restrict Syrian army and air force activity for subduing rebel action and wreaking violence on civilian populations.
debkafile’s sources disclose that the US President decided on this step after hearing Russian officials stating repeatedly that “Moscow would support the departure of President Bashar al-Assad if Syrians agreed to it.” This position was interpreted as opening up two paths of action:

The US operation would be modulated according to the way political and military events unfolded.
Washington is not sure how Moscow would react aside from sharp condemnations or whether Russia would accept a process of regime change in Damascus and its replacement by military rule.

Obama speeds up limited air strike, no-fly zones preparations for Syria