For anyone who has waited with identification and boarding pass in hand and inched through the long airport security process, the case of serial stowaway Marilyn Hartman is at once befuddling and disturbing.

Befuddling because the 66-year-old Grayslake woman has been arrested multiple times since at least 2010 for repeated attempts -- some successful -- to slip through screening and security, and board airplanes without a ticket.

Disturbing because while authorities say Hartman hasn't posed a risk to passengers and visitors, her actions underscore serious flaws in airport security. If a -- thankfully harmless -- woman who merely looks like a grandmother can slip through the system, think of what could happen if someone menacing decides to give it a try.

Hartman's latest incursions -- two arrests last month at O'Hare International Airport, including one that came after she allegedly had flown to London without a ticket or passport -- has prompted the Transportation Security Administration (TSA) to put security changes in place. These include altering passenger checkpoints to prevent people from circumventing TSA agents. More changes are being considered.

Officials won't elaborate on the changes or the effect on air travelers, but potential inconvenience is secondary to the need to close any security gaps that exist. Effective changes should be put into place quickly before a tragedy occurs.

"The security risk is that someone on the no-fly or (suspected terrorist) list could board a flight without the TSA knowing about it," airport security expert Jeff Price told our Russell Lissau.

Hartman, who has struggled with mental illness, has been arrested at least 14 times since 2010, including at least twice after she flew without a ticket. Her methods have varied, including once being stopped at a gate with a discarded boarding pass and another time when she sneaked past a security screener who was busy checking a family's documents. TSA says security changes have followed Hartman's attempts.

Some experts say she doesn't draw attention because she doesn't look like what people think a terrorist should look like.

Authorities won't say how she eluded security and flew to London despite being screened by TSA, indicating there was a failure in a layer of airport security. At least one occurred at the gate, because people aren't supposed to board a plane without valid passes. Watching flyers jostle for position during boarding provides a sense of how it could happen.

TSA officials say they are investigating whether more physical security measures should be added, and that they'll work with airlines to see if procedural changes are needed.

Clearly, these examinations are warranted. The security net must be tight enough that not even a harmless-looking sexagenarian can slip through.