multlined

\documentclass{article}
\usepackage[]{mathtools}
\begin{document}
\begin{align*}
  A & = \begin{multlined}[t]
    a + b + c + d + e + a + b + c + d + e \\
    + a + b + c + d + e + a + b + c + d + e
  \end{multlined}
  \\
  B & = \begin{multlined}[t]
    a + b + c + d + e + a + b + c + d \\
    + e + a + b + c + d + e + a
  \end{multlined}
\end{align*}
\end{document}