On June 28, terrorists entered Istanbul's airport and opened fire on travelers, before detonating explosives that killed 45 people and left more than 200 injured. The attack came just three months after a similar attack on Brussels Airport in Belgium, which also resulted in numerous injuries and a number of deaths.

Since September 11, airport security efforts have emphasized securing aircraft against hijackings, but the Brussels and Istanbul bombings highlighted other vulnerabilities. As these attacks demonstrate, it's not just planes that are vulnerable. Both the Brussels and Istanbul attacks sought to exploit the largely unprotected areas outside of the principal security checkpoints, where the attackers could detonate bombs outside of screening.

The large crowds of people who congregate in unsecured areas of an airport -- like security checkpoints, check-in counters, and baggage claim -- make appealing targets for terrorists, who like nothing better than maximum loss of life with minimum effort.

This week, the Senate passed the Federal Aviation Administration Reauthorization bill, which directly addresses these security vulnerabilities.

This legislation passed with overwhelming support from both parties, and we expect the President to sign it into law immediately. The reforms in this legislation -- the product of months of work at the Senate Commerce Committee that began long before the attacks -- will help ensure that attacks like those that happened in Brussels and Istanbul don't happen at American airports.

To address the tempting terrorist target offered by large crowds of people in unsecured areas of airports, the FAA bill includes provisions to get more Americans enrolled in the TSA's PreCheck program, which will help reduce the size of crowds by reducing wait times at security.

It also requires more effective deployment of TSA personnel to reduce wait times at checkpoints, and it requires the TSA to develop and test new security systems to expedite the movement of passengers. It also adds more prevention and response security teams and expands training for local airport security personnel, so that airports are better prepared to deter and respond to bombers or active-shooter threats.

In addition to securing U.S. airports, part of protecting the traveling public is making sure that Americans traveling to other countries are safe when they return to the U.S. Americans travel internationally on a regular basis, and on their return flights they depend on the quality of airport security in other countries.

To increase security for Americans traveling abroad, the FAA bill authorizes the TSA to donate unneeded screening equipment to foreign airports with direct flights to the United States. It authorizes the TSA to support training for foreign airport security personnel, and it requires the TSA to conduct assessments of security at foreign airports and of foreign cargo security programs.

Another aspect of airport security that has received less attention, but that is equally important, is the need to make sure that individuals who work behind the scenes at airports don't pose a threat.

In October 2015, terrorists killed 224 people when they brought down Russian Metrojet Flight 9268 shortly after it departed Sharm el-Sheikh airport in Egypt. Many experts believe that the terrorists responsible had help from an airport worker.

Clearly, ensuring that airport workers are trustworthy is essential to keeping passengers safe. However, at times the security badges that permit individuals to work behind the scenes at airports have been issued to individuals who have no business holding them.

Right now in the United States, individuals with convictions for crimes including embezzlement, sabotage, racketeering, immigration violations and assault with a deadly weapon can all obtain security badges granting them access to restricted sections of an airport.

While most criminals are not terrorists, there are too many criminals who would happily expand their criminal activity for the right price, even if it involved assisting terrorists.

In March of this year, for example, an airline ramp agent was arrested at a Florida airport with $282,400 in cash that he allegedly intended to hand off to an unknown individual. News reports suggested that he was aware the money was connected to illegal activity, but knew little else. In other words, he could easily have been transporting money for terrorists without knowing it.

The FAA bill tightens vetting of anyone with access to secure areas of an airport and expands the list of criminal convictions that could disqualify someone from holding a security badge. This bill also provides for an increase in random searches of behind-the-scenes airport workers, who are not always subject to security screening the way passengers are.

Since we took control of the Senate in January of 2015, Republicans have focused on passing legislation to address the challenges facing our country. I'm proud that with this bill, we've found a way to make our increasingly dangerous world a little safer for Americans.

Of course, as the horrific attacks in Nice remind us, airports are by no means the only target of those wanting to kill large numbers of people. But terrorists have consistently shown a determination to attack aviation targets. With this in mind, the FAA bill is the most significant airport security package in a decade, and it will help us make real progress toward keeping airline passengers safer.

It's a good example of what can happen when Democrats and Republicans work together to get things done for the American people.