Related Theories

Cognitive Dissonance (CD)

This article has a useful summary of CD:

a powerful motive to maintain cognitive consistency can give rise to irrational and sometimes maladaptive behavior.

As mentioned earlier this bears some similarities to SCE, however, according to Arkes and Blumer (in reference to CD research):

Numerous studies have shown that once a subject is induced to expend effort on an onerous task, the task is revalued upward

This does not really seem to apply to Sunk Cost Effects:

There are differences...in dissonance research subjects who have no sufficient justification for performing an onerous task improve their attitude toward the task. In the sunk cost situation, on the other hand, it is unlikely that investors begin to enjoy their floundering investments.

Some aspects of dissonance may apply but it is not really a complete fit or explanation.

Entrapment Theory

Subjects in entrapment situations typically incur small, continuous losses as they seek or wait for an eventual goal. Brockner et al. cite the example of waiting for a bus. After a very long wait, should you decide to take a cab, thereby nullifying all the time you have spent waiting for the bus?

This is similar to the SCE in that the time you have already waited could be seen as being "sunk".

Continued investment could be an analogue to small continuous losses.

There are differences too.

Continuing to wait is not as irrational from an economic standpoint as most sunk cost examples.

If you wait long enough a bus will eventually arrive.

If you keep investing in the plane from the earlier example there is no guarantee that it will be a success.

Foot in the Door (FITD)/Low Ball (LB) Techniques

These are both versions of an old sales technique.

Getting someone to comply with an initial small request increases the likelihood that they will comply with a larger request later:

An example would be first having people sign a petition to encourage legislators to support safe driving laws. Later, the petition signers are asked to display on their lawn a large sign that reads, “Drive safely.”

The Low Ball technique is similar:

When the small and large requests are for the Same target behavior, the technique is called the “low-ball” procedure (Cialdini, Cacioppo, Bassett, & Miller, 1978). An example would be getting someone to agree to buy a car at a discounted price and then removing the discount. The initial decision to buy heightens willingness to buy later when the car is no longer a good deal.

This bears some superficial relation to Sunk Cost.

An investment which would be less likely to be made on it's own becomes more likely in the face of a previous investment.

There are differences though as Arkes and Blumer point out:

A major difference between the sunk cost effect and the two techniques is that compliance is the dependent variable with the two techniques. Compliance typically plays no role in the sunk cost effect.

Put simply compliance is responding to a request from another person.

This is different from what occurs in the SCE, as in that case the person is responding to their own internal request and an outside agency does not come into it.

It is believed that FITD/LB work on the basis of "self-perception" theory:

A person observes himself or herself complying with a request to support good driving or a charitable organization. The person then concludes, “I’m the sort of person who supports that cause.” This conclusion based on self-observation then results in a high level of compliance when the larger request is made later (Snyder & Cunningham, 1975).

This is not really consistent with the SCE.

Using the plane analogy it is unlikely that you would continue to invest in developing the plane merely because you are "the kind of person who invests in developing planes".