BEIRUT, Lebanon — Western security agencies fear al Qaeda may try to unleash a terror spectacular as a way to grab back the initiative and attention from its one-time affiliate and now-fierce rival, the self-described Islamic State (formerly ISIS), whose leaders over the weekend declared an Islamic “caliphate” in territories it controls in Syria and Iraq and demanded allegiance from jihadist factions worldwide.

U.S. officials say the Obama administration is preparing to ramp up airport security and has requested Western allies do the same as concerns mount that suicide bombers are in the late stages of planning attacks on American- and European-bound commercial flights.

A senior European security official told The Daily Beast there are fears as well that jihadists recently returned from fighting in Syria with al Qaeda affiliate Jabhat al-Nusra are conspiring to detonate bombs on railways and buses in major European capitals such as London and Paris.

It looks like it will be a long, difficult summer for travelers as, at a minimum, the rivalry between terror groups for top-dog status will be felt in the form of longer security lines at airports and a further proliferation of inconvenient rules about what you can carry on a plane.

The weekend declaration in an audio recording posted online by aides to Abu Bakr al-Baghdadi declaring him “the caliph” and “leader for Muslims everywhere” represents another slap in the face for al Qaeda. It claims that the IS leader swore allegiance to Ayman al-Zawahiri, Osama bin Laden’s successor, but, in fact, he has been locked in competition for the loyalty of jihadist factions.

Al Qaeda, which disavowed al-Baghdadi and his group over the winter for refusing to obey orders, has been eclipsed by its wayward affiliate, and the announcement of a caliphate puts further pressure on the terror organization to respond in the contest for the leadership of the global jihadist movement.

“If al Qaeda wants to reclaim some semblance of legitimacy, it will desperately pursue a major strike,” according to Mideast scholar Aaron Zelin in a research paper published by the Washington Institute for Near East Policy, a D.C.-based think tank. He argues al-Baghdadi has “opened up a lead on al Qaeda, which has a steep hill to climb just to stave off its own relative decline.”

Zelin says the most likely model for assaults on European transport systems would be the March 2004 Madrid train bombings and the coordinated suicide attacks in July 2005 in central London that targeted civilians using the London Underground and buses. The London bombings killed 52 civilians and wounded more than 700, while in Madrid the bombings of commuter trains killed 191 people and injured 1,800.

The blitzkrieg success of an IS-led Sunni insurgency in Iraq the past two weeks has prompted praise from several jihadist groups, some once seen as aspiring to al Qaeda membership. These include Libya’s Ansar al-Sharia, which allegedly played a key role in the 2012 attack on U.S. installations in Benghazi and the death of four Americans, including Ambassador Christopher Stevens.

The declaration of a caliphate is adding pressure to jihadists to throw in their lot with al-Baghdadi or al Qaeda, says Charles Lister, a Visiting Fellow with the Brookings Institution Doha Center. “Already, this new Islamic State has received statements of support and opposition from jihadist factions in Syria,” he says, and “this announcement poses a huge threat to al Qaeda and its longtime position of leadership of the international jihadist cause.”

The sharp competition among jihadist terror groups and the increased incentive for al Qaeda to do something to stem defections coincides with intelligence gathered by U.S. agencies that militants in the Middle East have been exploring a new generation of non-metallic explosives unlikely to be detected by current airport security equipment.

Europeans traveling to the U.S. are likely to undergo greater attention. In a weekend interview with ABC’s This Week, President Barack Obama highlighted the risks to the U.S. of “battle-hardened” militants with European passports. “We’ve seen Europeans who are sympathetic to their [the jihadists’] cause traveling into Syria and now may travel into Iraq, getting battle-hardened. Then they come back,” he said.

U.S. officials aren’t revealing what enhanced security measures may be introduced but private sector security advisers say there likely will be more random screenings at airports and more profiling (even if no one dares to call it such). Liquids, gels and paste will probably be banned in cabin luggage—a return to the 2006 ban imposed on all liquids and gels except baby formula and prescription medications in carry-on baggage.

That prohibition was imposed in response to the uncovering of an al Qaeda plot to detonate liquid explosives on board 10 transatlantic flights from Britain to North America.

U.S. intelligence sources in Washington say the most alarming aspect of the threat now is that al-Nusra appears to have teamed up with jihadists from al Qaeda in the Arabian Peninsula, which is active in Yemen and Saudi Arabia and has been the most persistent al Qaeda affiliate in efforts to bomb U.S.-bound passenger jets.

The group was behind the attempted Christmas Day bombing in 2009 of Northwest Airlines flight 253 by Umar Farouk Abdulmutallab, who bungled the detonation of explosives sewn into his underwear. And it claimed responsibility for a 2010 cargo plane bomb plot foiled by British intelligence.

Aside from an overhaul of airport security, the Obama administration’s major response to the jihadist threat has been to ask for $500 million to arm and train moderate rebels in the Syrian civil war in their fight not only against President Bashar al-Assad but in their battle with jihadists commanded by al-Baghdadi.

There are two drawbacks potentially with the Obama administration’s anti-IS strategy. The military aid destined for so-called moderate rebels risks being shared with al Qaeda affiliate al-Nusra, the group behind the current suicide bombing threat against U.S.-bound passenger jets. Al-Nusra has been fighting alongside Syrian rebel groups against IS. The fear of spillage was one of the reasons the administration held off arming Syrian rebels before.

Critics also argue the military assistance may be coming too late to bolster mainstream rebels. In its stunning advance across northern and western Iraq, IS has captured huge stores of arms, ammunition and other materiel as well as artillery and even helicopters. The equipment not only leaves the group more formidably armed but it gives IS plenty of weapons to trade with other Syrian rebels in return for their allegiance.