There was a time when money really flew. Around the turn of the millennium, I got to inspect a Bank of America data center in central San Francisco where clerks in rows scoured stacks of checks, fishing out the highest-value ones for priority handling. They punched in the numbers, then the checks were bundled up so the originals could be flown across the country.

The urban location seemed unlikely for that kind of facility, I remarked to the bank executive giving me a tour. Perhaps, but it had the advantage of being nearly the same distance from the Oakland and San Francisco airports, he told me. If one airport was shut, the checks could be routed to another. That’s how important it was to ship those stacks of paper around.

Twenty-one years ago, 9/11 grounded the country’s fleet of airplanes. Checks piled up, and the Federal Reserve had to float the banking system, fronting tens of billions of dollars. When the country’s airspace reopened, groaning cargo planes chartered by banks sped the financial instruments to their destinations.

• The nation’s money crisis was brief, but it persuaded legislators that the economy couldn’t keep running on paper. The Check 21 Act passed in 2003 and allowed digitized copies of checks to serve in the place of the originals.
• By 2010, Bank of America had sold its data center. Before long, Square and Uber, two paragons of instant digital transactions, were renting offices there.
• Paper checks still persist, particularly in business transactions. But no one’s flying them around. AirNet Systems, a cargo airline that once specialized in transporting checks, was sold for $28.7 million in 2008 to private equity buyers.

The terror attacks turbocharged other tech businesses. Telecommuting and security firms got a boost.

• Shares of Webex (later bought by Cisco) and Polycom (now Poly) surged in the month after the attacks.
• Anthrax-laced letters sent in 2001 to politicians and media outlets led to a six-month backlog in mail deliveries in Washington. That gave a push to digitize government services.
• It took years for business travel to recover, as companies considered whether they could substitute videoconferences for trips.

Now, another disaster has fast-forwarded technology adoption. Looking back at the legacy of 9/11 is useful in considering which parts of the response to a crisis are temporary and which are permanent.

• There’s no going back to paper checks. Payments have been digitized — thanks in part to companies like Square, now Block — and may soon be instant, if plans by the Federal Reserve and private banking groups come to fruition.
• Telecommuting, as remote work was known a couple of decades ago, fell out of favor. By 2013, then-Yahoo CEO Marissa Mayer more or less banned working from home. But even before the pandemic, remote work advocates were making their counterargument. Telework technology is far more advanced, and employees are far more comfortable with it, but there may be more swings in attitudes toward work locations ahead.

The 9/11 Tribute Museum closed last month, in part due to the pandemic — one tragedy causing another’s legacy to fade. Americans famously have short memories, and Silicon Valley prefers to face toward the future. But the past has lessons, if only we can bring ourselves to remember what they are.

— Owen Thomas