以下是为什么航班恢复正常可能需要数天的原因：数百架飞机处于错误位置，机组人员工时已满，重启全国航班系统绝非易事。
Here’s Why It Could Take Days for Flights to Return to Normal With hundreds of planes out of position and crews out of hours, restarting the nation’s flight system is no easy task.
全国空域的近乎全面关闭于周五晚间结束，但其连锁反应延续到了周六，航空公司取消了数千个航班。
The near-total shutdown of the nation’s airspace ended on Friday evening, but its ripple effects continued into Saturday as airlines canceled thousands of flights.
到周六上午，当天近15%的航班已被取消，且这一数字仍在攀升。恢复工作极可能持续数天，因为航空公司正努力调整时刻表、为乘客改签以及调度飞机。
By Saturday morning, almost 15 percent of the day’s flights had been scrapped, and the number was still climbing. The recovery will most likely last for days as airlines work to juggle their schedules, rebook passengers and reposition planes.
航空运作如同接力赛。要运行良好，许多要素必须在同一时间、同一地点对齐，包括飞机、机组人员和空闲登机口的可用性。
Aviation functions like a relay race. To work well, many things have to align in the same place at the same time, including the availability of planes, crews and an open airport gate.
周五，数千架飞机被从空中拉回，填满了有限的地面空间。据航空数据公司Cirium称，许多飞机返回了它们刚起飞的机场。拥挤机场的喷气式客机不获准起飞，只能闲置等待，而机组人员迅速达到了法定工作时限。
On Friday, thousands of planes were pulled from the air, filling up limited space on the ground. Many returned to the airports they had just left, according to Cirium, an aviation data firm. Jets at crowded airports weren’t allowed to depart and sat idle while flight crews quickly hit their legal working limits.
飞行员通常限飞8至9小时，总值班时长为9至14小时，尽管工会合同和航空公司政策往往会进一步压缩这些时段。空乘人员也受值班时长限制。两者在值班间隔期间都必须获得漫长的休息。
Pilots are generally limited to eight or nine hours of flying and a total shift length of 9 to 14 hours, though union contracts and airline policies often shrink those windows. Flight attendants are also governed by limits on the length of their shift. Both must receive lengthy breaks in between shifts, too.
例如，一名原定周五晚间执飞纽约至迈阿密航班的飞行员，在等待地面停飞令解除时极易工时耗尽。这将使航空公司不仅难以为从纽约出发的航班寻找替补飞行员，也难以为该飞行员周六原定从迈阿密执飞的航班找到替补。这种情况乘以数百，航空公司时刻表便会迅速崩塌。
For instance, a pilot who was scheduled to fly from New York to Miami on Friday night could easily have timed out while waiting for the ground stop to end. That would have left the airline struggling to find replacement pilots not only for the flight from New York, but also for the flight that pilot was scheduled to operate out of Miami on Saturday. Multiply that by hundreds and airline schedules can quickly implode.
以 N865DN 为例，这是达美航空运营的一架波音 737 的尾号。根据航班追踪服务 Flightradar24 的数据，该机周五从南卡罗来纳州查尔斯顿起飞前往亚特兰大。随后，它又分别往返飞往肯塔基州路易斯维尔和弗吉尼亚州诺福克，最后返回亚特兰大。
Take N865DN, the tail number for a Boeing 737 operated by Delta Air Lines. It started Friday flying from Charleston, S.C., to Atlanta. From there, it made round trip flights to Louisville, Ky., and Norfolk, Va., returning to Atlanta, according to Flightradar24, a flight-tracking service.
原计划该机接下来飞往佐治亚州萨凡纳，再返回亚特兰大，然后飞往芝加哥，于周六在那里开始新一天的飞行。但这最后三个航段均未执行。
The plane was supposed to fly on to Savannah, Ga., back to Atlanta, and then to Chicago, where it would start the day on Saturday. But it never made those last three flights.
达美航空重新调整了周六的计划，安排该机从亚特兰大飞往华盛顿州斯波坎，随后前往盐湖城和北卡罗来纳州罗利-达勒姆。
Delta rebuilt its Saturday plan, with the plane scheduled to fly from Atlanta to Spokane, Wash., and on to Salt Lake City and Raleigh-Durham, N.C.
对于轻微的中断，航空公司可以通过重启航班、设法弥补损失的时间来追赶进度。但对于周五发生的这种大规模中断，通常需要通过主动取消大量航班来重置网络。
For minor disruptions, airlines can play catch-up by restarting flights and trying to make up for lost time. But bigger disruptions, such as the one that occurred Friday, often require resetting the network by proactively canceling many flights.
Niraj Chokshi 是《纽约时报》记者，撰写航空、铁路及其他交通运输行业报道。
Niraj Chokshi is a Times reporter who writes about aviation, rail and other transportation industries.