Considered essential to national security, Transportation Security Administration (TSA) officers are expected to work without pay through the partial government shutdown.

However, hundreds of TSA agents are currently staging what appears to be an impromptu protest, calling in sick rather than reporting in to work without pay.

Hydrick Thomas, president of the national TSA employee union told CNN, “This will definitely affect the flying public who we (are) sworn to protect.” According to Thomas, 170 TSA employees have called in at John F. Kennedy International Airport each day this week. At Dallas-Fort Worth International (DFW), the number of TSA employees calling in has increased by 200%-300%.

While union officials have stated the absences aren’t part of any officially organized action, they do believe that those numbers will continue to increase while the shutdown lasts.

That could be a very long time. Earlier today, President Trump threatened to keep the shutdown going for, “months or even years,” suggesting that he could keep it shut down until the 2020 Presidential election. Later, he also stated that he is considering declaring a national emergency in order to gain the unilateral power necessary for him to build a wall without congressional approval.

Meanwhile, the TSA call ours are only expected to get worse. According to a union official at DFW, “This problem of call outs is really going to explode over the next week or two when employees miss their first paycheck.”

According to union officials, it’s not just a protest. Many agents may be calling in sick because they can’t afford their child care, or because they need to find temporary jobs outside of the government in order to make ends meet.

As more TSA officials call out, the security of flights could be at risk. Faced with the potential of long security lines that could frustrate travelers, some airports may choose to skip on security measures such as random pat down security checks. They may also may offer expedited screening to passengers who haven’t been vetted.

However, whether these measures will be necessary remains to be seen.