Align - invisible equals sign?

The use of & is not restricted to the equality symbol. You can align prepending & to any character to serve as alignment point:

\documentclass{article}
\usepackage{amsmath}

\begin{document}

No alignment:
\begin{gather}
bci-ax+i > n\\
\sin(\theta_B) \rightarrow 9x
\end{gather}

Alignment at \verb+>+ and \verb+\rightarrow+:
\begin{align}
bci-ax+i &> n\\
\sin(\theta_B) &\rightarrow 9x
\end{align}

\end{document}