The airfield is in the Hasakah region, where American-backed militias have been mounting offensive operations against Islamic State-held territory northeast of the extremist group's stronghold in Raqqa.
It is also near a key supply line connecting Raqqa to the Islamic State group's second major city, Mosul, Iraq. Cutting that supply line is a key piece of the current American strategy for defeating the group.
Control of the airfield would help U.S. troops expedite delivery of weapons and ammunition to the region as well as operate more aircraft such as medevac helicopters, armed drones or intelligence, surveillance and reconnaissance platforms.
Imagery Supports Claims of U.S. Military Activity in Syria

Analysis

January 22, 2016 "Information Clearing House" - "Stratfor " -  As Syria's rebel coalition expands its fight against the Islamic State, so too does it appear that the United States is expanding its support of the rebels. Low-resolution satellite imagery taken Dec. 28 shows construction underway to extend the runway at an airfield in Rmeilan, al-Hasaka province, which would prepare the site to accommodate larger aircraft. (Similar images captured over the course of the last few weeks had been obscured by cloud cover, making it difficult to discern more recent ground activity.) Rumors of the U.S. arrival at Rmeilan originally surfaced in early January; the images confirm that at least some of those rumors are true.
Before the war, the airfield was an agricultural airstrip used by the Syrian government. As such, its runway was only 2,300 feet (700 meters) long, a length that appears to be doubling. The airfield has since been captured by the Kurdish People's Protection Units (YPG), which has controlled the airport for more than two years.

The new and improved infrastructure could help the Syrian Democratic Forces conduct offensive operations against the Islamic State. The United States has already carried out two weapons airdrops to the rebel Syrian Arab Coalition, a faction of the Syrian Democratic Forces. But additional assistance in the Syrian Democratic Forces' fight against the Islamic State, including efforts to drive the extremist group from its self-declared capital in Raqqa, would require a broader logistical effort than is currently underway. Expanding the Rmeilan runway could expedite this process by allowing U.S. airplanes to land and drop off supplies instead of continuing to rely on airdrops.
The U.S. involvement in al-Hasaka province would not be so unusual; the United States nearly always attempts to establish an air bridge to support the semi-permanent positions of the conflicts in which it operates. But it comes at a time when Russia similarly builds up its own military presence there. A Russian detachment composed of logistics personnel and military intelligence officers has reportedly arrived in Qamishli airport, an airfield in al-Hasaka controlled by forces loyal to the Syrian government. While the Russians will likely try to improve the logistical capability of the airfield, they have reportedly already sought to enhance their influence with the various rebel militia groups operating in the province.


Link: http://www.informationclearinghouse.info/article44015.htm