NEW YORK (TheStreet) -- While one of Warren Buffett's greatest strengths is his ability to pick out "sure things," not all of bets he has made throughout his career have paid off. In fact, there are a number of investments the Oracle of Omaha has tried his luck with that have done more harm than good.

His bets on the airline industry, Conoco-Phillips ( COP) ando , and Moody's ( MCO) come to mind when mulling particular Warren Buffett investment blunders. All three investments can be seen as stains on his otherwise stellar career.

U.S. Airways is often highlighted as one of Buffett's most costly slip-ups when, in 1995, the investor was forced to write of 75% of his $385 million investment in the firm.

Despite this staggering loss with U.S. Airways, Buffett has not given up on the airline industry. He currently owns NetJets, a fractional jet sharing program. Like his previous experience, this airline company has resulted in numerous headaches for Buffett.

Hoping to turn the company into a profitable venture, he shook up the company's management in 2009, firing CEO, Rick Santulli and replacing him with rumored Buffett successor, David Sokol. It will be interesting to see if Buffett will eventually shed this company from the Berkshire Hathaway ( BRK.A) portfolio.

Conoco-Phillips is another investment Buffett may wish he could take back. The investor first started buying shares of this oil giant in early 2006. His position was dramatically increased in 2008 when Buffett attempted to take advantage of oil prices which, at the time, were rocketing higher.

Unfortunately, the timing of this bet was terrible. When oil prices returned to earth, shares of COP followed suit, resulting in a several billion dollar hit for Berkshire Hathaway.

Whereas U.S. Airways and Conoco-Phillips are notable mistakes due to their monetary damage to Buffett, the Oracle's investment in Moody's has dealt damage to the investor's reputation.

In the aftermath of this most recent economic crisis, Buffett has been noticeably indecisive in his views towards this troubled ratings agency. While he has expressed his disappointment in the company's actions leading up to the meltdown and has been slowly chipping away at his company's stake in MCO, when he was issued a subpoena to appear in front of the Financial Crisis Inquiry Commission, he offered support for the firm, insisting that while they may have made mistakes, no one foresaw the crisis.

All three of these investments can be considered big blunders. However, none earn the top spot in Buffett's mind. What Buffett personally considers to be his biggest slip-up is surprising.

This week, sitting down with CNBC's Becky Quick, Warren Buffett was asked what he considered to be his biggest mistake made during his illustrious investing career.

Unexpectedly, rather than pointing to duds such as Conoco-Phillips, Moody's or United Airways (LCC), Buffett singled out Berkshire Hathaway, the textile-company-turned-investment-empire, which has been the base for propelling Buffett to the top of the ranks among the world's wealthiest individuals.

Looking back on the deal, Buffett explained that it was not the firm's fundamentals which triggered his desire to buy control of the company. Rather, the move was emotionally driven. In 1964, when he already owned a fair share of the firm, he felt that he got ripped off by the management. Seeking vengeance, when he managed take the reigns of the firm he fired the individual who had scammed him.

The underlying motive behind his decision to purchase Berkshire Hathaway is why he considers it to be his biggest blunder. Buffett is a strong proponent of leaving out emotions when it comes to investing. In this situation, this belief was cast aside.

Buffett's mistakes highlight the fact that no one is perfect when it comes to investing. While losses can be tough to stomach, it is important not to become dissuaded. Most of the time, there are lessons that come out of these less than pleasant times.

Written by Don Dion in Williamstown, Mass.

At the time of publication, Dion Money Management was not long any of the equities mentioned.

Don Dion is president and founder of Dion Money Management, a fee-based investment advisory firm to affluent individuals, families and nonprofit organizations, where he is responsible for setting investment policy, creating custom portfolios and overseeing the performance of client accounts. Founded in 1996 and based in Williamstown, Mass., Dion Money Management manages assets for clients in 49 states and 11 countries. Dion is a licensed attorney in Massachusetts and Maine and has more than 25 years' experience working in the financial markets, having founded and run two publicly traded companies before establishing Dion Money Management.

Dion also is publisher of the Fidelity Independent Adviser family of newsletters, which provides to a broad range of investors his commentary on the financial markets, with a specific emphasis on mutual funds and exchange-traded funds. With more than 100,000 subscribers in the U.S. and 29 other countries, Fidelity Independent Adviser publishes six monthly newsletters and three weekly newsletters. Its flagship publication, Fidelity Independent Adviser, has been published monthly for 11 years and reaches 40,000 subscribers.

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