One of the most unusual bombings occurred on December 29, 1975 at LaGuardia Airport in New York. Around 6 pm a large bomb placed in a locker in the baggage claim area exploded, killing 11 and wounding over 70. The case has never been solved. Nobody ever took formal credit.
Online research of this event doesn't provide much. New York terrorism investigators had a person of interest, a lone nut Croatian who had placed a bomb in a locker in Grand Central Station a year later while also hijacking a TWA flight between LaGuardia and Chicago. Since the LGA bomb blast occurred at the Eastern/TWA baggage claim it's no wonder they suspected him. He steadfastly denied it over the years, right up to his parole and deportation back to free Croatia in 2008. But he seems a good target.
One reason he seemed a good target is that investigators generally took the lack of formal claim to mean the bomber(s) didn't intend deaths, just a loud statement. This might have fit a Croatian terrorist trying to gain freedom for his people. At the time of the blast former Israeli premier Golda Meir was visiting New York so that angle was considered, but apparently dropped. They ruled out the bomb being meant to target any one individual in the airport (it would have been nearly impossible without a remote controller anyway). Investigators immediately suspected FALN, The Jewish Defense League, and the PLO but surely those groups would have taken credit had they been responsible.
Yet there was one group operating in the mid 70s out of the New York area that didn't seem to get mentioned--the Weather Underground. Their public statements--both then and now--downplay the death/injury objective of their bombs and play up the bang to make a point objective, which would also fit the no claim of credit. Were they ever suspected?
According to this Wiki timeline the WUG took credit for 3 bombings in 1975 before the LaGuardia blast...
January 29 - Bombing of the State Department; WUO states this is in response to escalation in Vietnam. (AP. "State Department Rattled by Blast," The Daily Times-News, January 29, 1975, p. 1)
January 23 - Offices of Dept. of Defense in Oakland are bombed. In a statement released to the press, Weather expressed solidarity with the Vietnamese still fighting against the Thieu regime in Vietnam. 
Spring - WUO publishes "Politics in Command," which is its new political-military strategy. It furthers the line of building a legal, above-ground organization and begins to minimize the armed struggle role.
March – The WUO releases its first edition of a new magazine entitled Osawatomie.
June 16 - Weathermen bomb a Banco de Ponce (a Puerto Rican bank) in New York, WUO states this is in solidarity with striking Puerto Rican cement workers.
July - More than a thousand women attend the Socialist Feminist Conference at Antioch College in Yellow Springs, OH in which WUO supporters attempt to play a major role.
July 11-13 – The Prairie Fire Organizing Committee (PFOC) holds its first national convention during which time they go through the formality of creating a new organization.
September – Bombing of the Kennecott Corporation; WUO states this is in retribution for Kennecott's alleged involvement in the Chilean coup two years prior.So they were active in the year leading up to the event. For some reason the Times interview with the former bomb squad investigator didn't mention them, not even to say they were considered but ruled out.
The "COINTELPRO" scandal (domestic warrantless wiretapping to follow revolutionary groups prevalent during the Vietnam war) occurred in 1971, which led to federal charges against WUG suspects being dropped. We also know the FBI had a mole in the group at some point. Bill Ayers and his wife Bernadine had gone underground in the early 70s and were still there in 75, having just released their own communist manifesto dedicated to Mao and Satan called "Prairie Fire" a year earlier.
The WUG was not a group of yahoos. They actually took credit for bombing the State Department at Foggy Bottom in late January 1975. They had previously bombed the Pentagon. No child's play. They also bombed a DoD office and a bank later that year, then a corporation.
Then for some reason the group "slowly disbands" beginning in 1976 with many members turning themselves in over the next few years to take advantage of an amnesty program brought about by Jimmy Carter. According to Ayers the group split about that same time, with a more radical faction carrying on after a merger with a black separatist group (later carried out the Brinks robbery in 1981). So what triggered this sudden split in 1976?
Conventional wisdom says it was because the war in Vietnam had finally ended. Yet our evacuation from Saigon occurred in April 1975 while the group still bombed Kennecott Corporation in September of that year, supposedly in retaliation for their involvement in a Chilean coup. Ayers and others have said the end of the war caused the group to begin to split apart--the quintessential rebels without a cause--at least on the surface. But as Prairie Fire illustrates their war wasn't just over the Vietnam conflict but against capitalism at large. Ayers still admits this today. Yet for some reason their bombing philosophy basically ended at some point towards the end of 1975 leading to a split. Why?
This is not some whackadoodle post to suggest the FBI knew about bombings and did nothing, or God forbid were involved in the LaGuardia bombing--the mole was apparently only a go-between operating between central HQ and field units. The government would have been derelict of duty had they NOT investigated a group whose mission statement was to overthrow the government. There's reason to believe that communist Cuba was helping to fund the Weathermen, which is not to say Cuba was involved directly in any bombings, but it's not to say they weren't either. Perhaps there was an international or domestic angle the government didn't want publicized at the time, ie an entity sending a silent message, who knows.
Since this post is about the Weathermen it's also not designed to link Obama to any terrorism. He was in Hawaii at the time, 14 years old or so--yes, evidently being mentored by a communist but there's no known link between Davis and Ayers. And yes, he started his political career in Ayers' living room and the campaign deceived voters about their relationship, but that can also be explained by the radioactivity of Ayers outside of liberal academia (in bitter clinger America), which would amount to a political distancing without culpability. Then again, the radioactivity would have been considerably higher.
No, this post is merely from a guy sitting around in his underwear bringing to light a very strange chapter of terrorism history in America and asking a question--were the Weathermen ever considered suspects and if not, why not?