It was a day that changed America.

The fallout from “9/11” reverberated across the nation, affecting everything from politics and foreign affairs to the economy.

But few things changed more for Americans that the way we fly. Even 25 years since 9/11, the day’s impact on aviation has been a lasting one.

As the attacks unfolded, air traffic controllers and airline personnel scrambled to figure out what was happening, which ultimately culminated in the first (and to this date, only) complete closure of U.S. airspace.

But once planes took the air again, the passenger experience on the ground rapidly evolved.

Major security overhaul

In the weeks and months that followed 9/11, new security protocols were rolled out at airports nationwide. Gate areas were restricted to ticketed passengers only. No more welcoming loved ones at the gate.

As those security perimeters pushed out, a federalized workforce – the Transportation Security Administration – was created to manage secure spaces at U.S. airports and other important travel nodes. This was a major shift from the private companies tasked with securing our skies before 9/11.

Of course, it wasn’t just the terrorist attacks of that day that brought about changes. The nation’s security apparatus continued to evolve as new potential threats emerged.

• Dec. 2001: Richard Reid attempted to ignite an explosive device hidden in his shoe, leading to new procedures that required passengers to remove their shoes when proceeding through checkpoints.
• Aug. 2006: A foiled plot involving liquid explosives on U.S.-bound flights led to new restrictions on the size of liquids allowed in carry-on luggage, which eventually became the 3-1-1 rule that remains in effect to this day.
• Dec. 2009: A Nigerian national gained notoriety when he tried to detonate a device sewn into his underwear, leading to the installation of full-body scanners and more invasive pat-down procedures at airports across the U.S.

While this increasingly stringent screening process created plenty of frustration for flyers, the post-9/11 years also saw the emergence of new trusted traveler programs — beginning with Global Entry, which launched as a small pilot program at three airports on June 6, 2008, before becoming a permanent program of the Department of Homeland Security (DHS) on March 7, 2012. Applicants undergo a background check, and once approved as “low-risk” travelers, they can enjoy expedited entry into the U.S. after arriving from an international destination.

Around that same time, another notable innovation officially launched at Las Vegas’ Harry Reid International Airport (LAS) in Dec. 2011: TSA PreCheck.

Originally extended for free to frequent flyers on select airlines, the program now offers paid membership for travelers to enjoy quicker, less-intensive screening at U.S. airports.

Even Real ID traces its roots back to the attacks, as it was originally passed in 2005 based on recommendations from the 9/11 commission to standardize state-issued identification.

That innovation continues today, with new technologies like Touchless ID, Clear and eGates to enable even quicker passenger screening.

Financial ramifications

Security may have been at the forefront, but 9/11 also helped accelerate the industry’s shift from a highly regulated model to the free-market version we know today.

The near-immediate collapse in air travel demand dealt the industry a severe financial shock, even with up to $15 billion in federal bailout funds .

Planes flew nearly empty in the weeks following 9/11. Ronald Reagan Washington National Airport (DCA) remained shut down for weeks, dealing a massive financial blow to US Airways, the largest carrier there (which filed for bankruptcy protection in 2002 and again in 2004 before ultimately merging with America West in 2005).

Midway Airlines, a mid-size carrier based in North Carolina that was already teetering financially, abruptly went out of business. Elsewhere, layoffs swelled. Even bigger, established airlines went through bankruptcy-driven restructuring due to losses stemming from 9/11, including United, Delta and Northwest.

A series of mergers followed as airlines reorganized to become more powerful by combining with rivals while also streamlining redundant parts of their operations to boost profits. By the end of the 2010s, a dozen major airlines went through a cycle of tie-ups that left four big airlines (American, Delta, United and Southwest) controlling roughly 80% of the U.S. market.

Around the same time, airlines began looking for financial lifelines as cash reserves dwindled. They got it from banks willing to buy miles by the millions that they could then dole out to customers holding their cobranded airline credit cards.

It’s a trend that’s grown, hastened further by the financial crisis of 2008-09. Today, airlines make millions of dollars in revenue just from their bank deals on cobranded credit cards.

But it wasn’t all about dollars and cents.

The personal side of the attacks

It’s impossible to talk about 9/11 without acknowledging the incredible human toll of the attacks. Nearly 3,000 people perished that day, and many more have been impacted with the loss of loved ones — or with lingering health issues from rescue and recovery efforts at Ground Zero.

For the aviation industry, the 246 innocent men and women on the four hijacked planes were more than just a number. They were husbands and wives, fathers and mothers, sons and daughters. They were our neighbors, our friends, our coworkers, going about their daily lives when the most mundane of circumstances — a cross-country flight on a Tuesday morning — turned into a tragedy.

But those individuals didn’t go out quietly. Flight attendants alerted their operations teams from the back of the planes. Passengers called their loved ones. And the 40 brave souls onboard United Flight 93 made the ultimate sacrifice when they stormed the cockpit and forced their aircraft down in rural Pennsylvania, preventing a terrible day from getting even worse.

It is these travelers that we honor here today.

Twenty-five years ago, 33 airline crew members and 213 passengers took to the skies, not knowing it would be their final flight.

Here at The Points Guy, we recognize that travel is a privilege to be cherished. With every trip we take, we make memories that so many no longer can. And we will continue to board those planes, not in spite of what happened that September morning, but because we will not take the gift of travel for granted.

We remember them, and we fly on.