During the dispute, Ms Saiyed compared asking her to remove the Palestinian badge to forcing a Muslim woman to take off her hijab.
But after hearing just under two weeks of evidence, and considering more than 1,600 pages of documents, the tribunal unanimously dismissed all of her claims against Heathrow Airport Ltd.
Ms Saiyed, a Muslim security officer who has previously been a Unite Union rep, lodged a formal grievance the day after the incident, arguing the flag was an important expression of her identity and beliefs, and that asking her to remove it amounted to discrimination.
It caused a row which led to Ms Saiyed submitting more complaints.
She wrote to bosses stating: "Demanding the removal of the Palestinian flag from my lanyard is tantamount to finding my hijab offensive and insisting on its removal."
The tribunal heard she went on to raise a number of grievances and complaints about the way the airport dealt with the dispute, including allegations relating to internal meetings, diversity events, communications with managers and the decision not to publish a Ramadan video in which she had appeared.
The tribunal found that Heathrow had repeatedly investigated her complaints, met with her on numerous occasions and sought to resolve the issues she raised.
The judgment said: "We find that the claimant is capable of saying something and believing it is true and yet is shown to be wrong when you look at the contemporaneous documents."
It continued: "We find that this connects to the fact that the claimant in person is very polite and not aggressive. We find that she would not want to think that she would accuse anyone of racism or of being a racist as she would consider herself too polite."
The tribunal added: "We find that the claimant is a very capable, intelligent individual, but someone whose evidence was not always credible and reliable."
The panel found there was no evidence that Heathrow's actions had been motivated by Ms Saiyed's race or religion, concluding that the decisions complained of were management responses to an increasingly complex workplace dispute rather than acts of unlawful discrimination.
It dismissed all of Ms Saiyed's claims of direct race discrimination, direct religious discrimination, harassment and victimisation.
Concluding, the tribunal ruled that while Ms Saiyed genuinely believed she had been wronged, the evidence simply did not support the serious allegations she had made against her employer.
'Free Palestine' badges (Getty Images)Getty Images
The dispute unfolded against a backdrop of wider controversy over Palestinian symbols worn by Heathrow staff following the outbreak of the Gaza war.
In June 2024, five security officers were removed from screening an El Al flight to Tel Aviv after passengers complained they felt intimidated by Palestinian flag and watermelon badges worn on their uniforms.
Heathrow said at the time that all passengers should feel "safe and welcome" at the airport and stressed that staff were expected to follow its uniform policy, with any unauthorised items being removed.
The airport later reiterated that political badges were not part of its approved uniform and confirmed it would ensure the rules were enforced.
